2024-03-28T20:19:55Z
http://digitalcommons.unl.edu/do/oai/
oai:digitalcommons.unl.edu:physicsfacpub-1019
2017-03-24T13:29:53Z
publication:physicsfacpub
publication:mrsecfacpubs
publication:physicsresearch
publication:physics
publication:physicsbinek
publication:materialsresearchscieeng
Exchange Bias Training Effect in Coupled All Ferromagnetic Bilayer Structures
Binek, Christian
Polisetty, Srinivas
He, Xi
Berger, A.
Exchange coupled bilayers of soft and hard ferromagnetic thin films show remarkable analogies to conventional antiferromagnetic/ferromagnetic exchange bias heterostructures. Not only do all these ferromagnetic bilayers exhibit a tunable exchange bias effect, they also show a distinct training behavior upon cycling the soft layer through consecutive hysteresis loops. In contrast with conventional exchange bias systems, such all ferromagnetic bilayer structures allow the observation of training induced changes in the bias-setting hardmagnetic layer by means of simple magnetometry. Our experiments show unambiguously that the exchange bias training effect is driven by deviations from equilibrium in the pinning layer. A comparison of our experimental data with predictions from a theory based upon triggered relaxation phenomena shows excellent agreement.
2006-02-13T08:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsfacpub/20
https://digitalcommons.unl.edu/context/physicsfacpub/article/1019/viewcontent/PRL_2006.pdf
Department of Physics and Astronomy: Faculty Publications
DigitalCommons@University of Nebraska - Lincoln
Physics
oai:digitalcommons.unl.edu:physicsfacpub-1020
2017-03-24T13:27:30Z
publication:physicsfacpub
publication:mrsecfacpubs
publication:physicsresearch
publication:physics
publication:physicsbinek
publication:materialsresearchscieeng
Temperature dependence of the training effect in a Co/CoO exchange-bias layer
Binek, Christian
He, Xi
Polisetty, Srinivas
The temperature dependence of the training effect is studied in a Co/CoO exchange-bias bilayer and a phenomenological theory is presented. After field cooling the sample to below its blocking temperature, the absolute value of the exchange-bias field decreases when cycling the heterostructure through consecutive hysteresis loops. This decrease is known as the training effect and is studied in the temperature range 5 < =T < =120 K. An implicit sequence, which has been recently derived using the Landau-Khalatnikov approach of relaxation, fits the respective data set for each individual temperature. The underlying discretized dynamic equation involves an expansion of the free energy in powers of the interface magnetization of the antiferromagnetic pinning layer. The particular structure of the free energy with a leading fourth-order term is derived in a mean-field approach. The explicit temperature dependence of the leading expansion coefficient explains the temperature dependence of the training effect. The analytic approach is confirmed by the result of a best fit, which condenses the data from more than 50 measured hysteresis loops.
2005-08-03T07:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsfacpub/21
https://digitalcommons.unl.edu/context/physicsfacpub/article/1020/viewcontent/PRB_2005.pdf
Department of Physics and Astronomy: Faculty Publications
DigitalCommons@University of Nebraska - Lincoln
Physics
oai:digitalcommons.unl.edu:physicsfacpub-1021
2017-03-30T11:05:16Z
publication:physicsfacpub
publication:mrsecfacpubs
publication:physicsresearch
publication:physics
publication:physicsbinek
publication:materialsresearchscieeng
Magnetoelectric Switching of Exchange Bias
Borisov, Pavel
Hochstrat, Andreas
Chen, Xi
Kleeman, Wolfgang
Binek, Christian
The perpendicular exchange bias field, HEB, of the magnetoelectric heterostructure Cr2O3(111)/(Co/Pt)3 changes sign after field cooling to below the Néel temperature of Cr2O3 in either parallel or antiparallel axial magnetic and electric freezing fields. The switching of HEB is explained by magnetoelectrically induced antiferromagnetic single domains which extend to the interface, where the direction of their end spins controls the sign of HEB. Novel applications in magnetoelectronic devices seem possible.
2005-03-23T08:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsfacpub/22
https://digitalcommons.unl.edu/context/physicsfacpub/article/1021/viewcontent/PRL_2005.pdf
Department of Physics and Astronomy: Faculty Publications
DigitalCommons@University of Nebraska - Lincoln
Physics
oai:digitalcommons.unl.edu:physicsfacpub-1059
2017-04-11T18:28:23Z
publication:chemistryredepenning
publication:physicsfacpub
publication:mrsecfacpubs
publication:physicsresearch
publication:chemfacpub
publication:physics
publication:chemistryresearch
publication:physicsbinek
publication:materialsresearchscieeng
publication:chemistry
Nonextensivity in magnetic nanoparticle ensembles
Binek, Christian
Polisetty, Srinivas
He, Xi
Mukherjee, Tathagata
Rajesh, Rajasekaran
Redepenning, Jody G.
A superconducting quantum interference device and Faraday rotation technique are used to study dipolar interacting nanoparticles embedded in a polystyrene matrix. Magnetization isotherms are measured for three cylindrically shaped samples of constant diameter but various heights. Detailed analysis of the isotherms supports Tsallis' conjecture of a magnetic equation of state that involves temperature and magnetic field variables scaled by the logarithm of the number of magnetic nanoparticles. This unusual scaling of thermodynamic variables, which are conventionally considered to be intensive, originates from the nonextensivity of the Gibbs free energy in three-dimensional dipolar interacting particle ensembles. Our experimental evidence for nonextensivity is based on the data collapse of various isotherms that require scaling of the field variable in accordance with Tsallis' equation of state.
2006-09-11T07:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsfacpub/60
https://digitalcommons.unl.edu/context/physicsfacpub/article/1059/viewcontent/PRB74_2006_054432.pdf
Department of Physics and Astronomy: Faculty Publications
DigitalCommons@University of Nebraska - Lincoln
nanoparticles
fundamental thermodynamics
nonextensivity
Physics
oai:digitalcommons.unl.edu:physicsbinek-1000
2008-07-28T16:26:03Z
publication:physicsresearch
publication:physics
publication:physicsbinek
Christian Binek: List of Publications
Lists citations for 60 published articles and one monograph by Christian Binek of the Department of Physics and Astronomy at the University of Nebraska-Lincoln. Includes some links. Current as of July 2008.
2008-07-28T07:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/1
https://digitalcommons.unl.edu/context/physicsbinek/article/1000/viewcontent/auto_convert.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Physics
oai:digitalcommons.unl.edu:physicsbinek-1001
2017-03-26T01:12:52Z
publication:physicsfacpub
publication:physicsresearch
publication:physics
publication:physicsbinek
Domainlike antiferromagnetic correlations of paramagnetic FeCl<sub>2</sub>: A field-induced Griffiths phase?
Binek, Christian
Kleemann, Wolfgang
Domainlike antiferromagnetic correlations are detected by SQUID measurements of the low-frequency susceptibility in the metamagnet FeCl2 when exposed to an axial magnetic field H at temperatures Tc (H)≤T≤TN. A distinct change of curvature of χ’’ vs T appearing at TN is explained in terms of fluctuating distributions of demagnetizing fields and, hence, transition temperatures. The field-induced dynamic domain phase—an analog of the Griffiths phase predicted for a ferromagnet with dilution x within Tc(x)≤T≤Tc(0)—is confirmed by elastic light scattering experiments.
1994-02-21T08:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/2
https://digitalcommons.unl.edu/context/physicsbinek/article/1001/viewcontent/1_Domainlike_antiferromagnetic_correlations_of_paramagnetic_FeCl2_A_field_induced_Griffiths_phase.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Physics
oai:digitalcommons.unl.edu:physicsbinek-1003
2017-03-27T01:17:20Z
publication:physicsfacpub
publication:physicsresearch
publication:physics
publication:physicsbinek
Interface alloying and magnetic properties of Fe/Rh multilayers
Hanisch, K.
Keune, W.
Brand, R.A.
Binek, Christian
Kleemann, Wolfman
Rh(20 Å)/57Fe(tFe) multilayers with Fe thicknesses tFe of 2, 5, 10, and 15 Å prepared by alternate evaporation in UHV have been investigated by x-ray diffraction (XRD), Mössbauer spectroscopy, and SQUID magnetometry. First- and second-order superstructure Bragg peaks (but no higher-order peaks) in small-angle XRD patterns suggest some compositional modulation. Mössbauer spectra taken at 4.2 K are characterized by a distribution P(Bhf) of hyperfine fields Bhf. Peaks observed in the P(Bhf) curves near 17 and 35 T are assigned to an fcc-RhFe interface alloy (~7–24 at. % Fe) with spin-glasslike properties and to a disordered ferromagnetic bcc-FeRh alloy (~96 at. % Fe), respectively. The magnetic transition temperature of the fcc alloy was found to be 23 and 45 K for tFe=2 and 5 Å, respectively, and Bhf follows a T3/2 law. For tFe=2 Å, spin-glasslike behavior was observed by magnetometry. Journal of Applied Physics is copyrighted by The American Institute of Physics.
1994-11-15T08:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/4
https://digitalcommons.unl.edu/context/physicsbinek/article/1003/viewcontent/3_Interface_alloying_and_magnetic_properties_of_FeRh_multilayers.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Physics
oai:digitalcommons.unl.edu:physicsbinek-1005
2017-03-27T01:16:05Z
publication:physicsfacpub
publication:physicsresearch
publication:physics
publication:physicsbinek
Local magnetic properties of antiferromagnetic FeBr<sub>2</sub>
Pelloth, J.
Brand, R.A.
Takele, S.
Pereira de Azevedo, M.M.
Kleemann, Wolfman
Binek, Christian
Kushauer, J.
Bertrand, D.
The antiferromagnet FeBr2 has been studied by Mössbauer spectroscopy in external fields both in the metamagnetic region below the multicritical temperature TMCP and in the second-order transition region above. The local magnetization shows that the metamagnetic transition occurs by spin flips, as in simple models. However, in the second-order transition region, the local magnetization of the sublattice oriented antiparallel to the external field varies continuously but remains parallel to the c axis. This can only be understood if the external magnetic field induces strong transversal spin precession of the moments on the antiparallel sublattice. This shows that the anomalous maxima in the imaginary part χ″ recently found in the ac susceptibility [M.M. Pereira de Azevedo et al., J. Magn. Magn. Mater. 140-144, 1557 (1995)] and denoted H- below the critical field Hc(T), and H+ above, can be understood as being caused by noncritical transversal spin fluctuations.
1995-12-01T08:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/6
https://digitalcommons.unl.edu/context/physicsbinek/article/1005/viewcontent/5_local_magnetic_properties_of_antiferromagnetic_FeBr2.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Physics
oai:digitalcommons.unl.edu:physicsbinek-1007
2017-03-26T11:09:01Z
publication:physicsfacpub
publication:physicsresearch
publication:physics
publication:physicsbinek
Magnetic neutron-scattering investigation of the field-induced Griffiths phase in FeCl<sub>2</sub>
Binek, Christian
Bertrand, D.
Regnault, L.P.
Kleemann, Wolfgang
Quasielastic neutron scattering has been utilized to investigate the Griffiths phase induced by an axial magnetic field in FeCl2 at temperatures Tc(H)⩽T⩽TN, where Tc(H) is the transition temperature in an external magnetic field H. We present the temperature dependence of the integrated neutron-scattering intensity at fixed scattering vectors for various magnetic fields. On cooling below TN the antiferromagnetic short-range fluctuations decrease due to an increase of the volume fraction which is already antiferromagnetically ordered. A weighted average of the local contributions to the antiferromagnetic susceptibility quantitatively describes the scattering cross section.
1996-10-01T07:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/8
https://digitalcommons.unl.edu/context/physicsbinek/article/1007/viewcontent/7_magnetic_neutron_scattering_investigation_of_the_field_induced_griffiths_phase_in_FeCl2.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Physics
oai:digitalcommons.unl.edu:physicsbinek-1009
2017-03-25T23:36:05Z
publication:physicsfacpub
publication:physicsresearch
publication:physics
publication:physicsbinek
Crossover from pure Ising to random-exchange dominated behavior of the two-dimensional antiferromagnet Rb<sub>2</sub>Co<sub>1-x</sub>Mg<sub>x</sub>F<sub>4</sub>
Binek, Christian
Kleemann, Wolfgang
Belanger, David P.
The temperature dependence of the uniform susceptibility χ of diluted two-dimensional Ising antiferromagnets Rb2Co1-xMgxF4, 0<~xN(x), but also in relation to the “local” phase transition temperatures TN′ throughout the Griffiths regime, TN(x)<~TN′<~TN(0), a satisfactory quantitative description of χ vs T is deduced for any x above the percolation threshold. ©1998 The American Physical Society
1998-04-01T08:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/10
https://digitalcommons.unl.edu/context/physicsbinek/article/1009/viewcontent/9_Crossover_from_pure_Ising_to_random_exchange_dominated_behavior_of_the_two_dimensional_antiferromagnet_Rb2Co1_xMgxF4.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Physics
oai:digitalcommons.unl.edu:physicsbinek-1002
2017-03-26T11:00:02Z
publication:physicsfacpub
publication:physicsresearch
publication:physics
publication:physicsbinek
Blocking of logarithmic temporal relaxation of magnetic remanence by piezomagnetically induced domains in Fe<sub>1-x</sub>Zn<sub>x</sub>F<sub>2</sub>
Kushauer, J.
Binek, Christian
Kleemann, Wolfgang
Faraday rotation and superconducting quantum interference device magnetometry were used to investigate the relaxation of the weak-field induced remanence, µ, of the random-field Ising model system Fe1-xZnxF2. The stretched logarithmic decay law, as predicted by Nattermann and Vilfan for the case of compact domains with fractal surfaces, was confirmed for freezing fields of 3≤B≤5 T. Virtually constant remanence, µ, was found at low fields, 0.0002≤B≤1.5 T. This ferrimagnetic moment is due to the piezomagnetic effect acting on random-stress induced immobile domains. Chemical etching, which removes surface stress originating from the sample preparation, proves to decrease the remanence by about 50%, part of which is restored after renewed optical polishing. Journal of Applied Physics is copyrighted by The American Institute of Physics.
1994-05-15T07:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/3
https://digitalcommons.unl.edu/context/physicsbinek/article/1002/viewcontent/2_Blocking_of_logarithmic_temporal_relaxation_of_magnetic_remanence_by_piezomagnetically_induced_domains_in_Fe1_xZnxF2.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Physics
oai:digitalcommons.unl.edu:physicsbinek-1004
2017-03-25T23:32:58Z
publication:physicsfacpub
publication:physicsresearch
publication:physics
publication:physicsbinek
Evidence of dilution-induced Griffiths instabilities in K<sub>2</sub>Cu<sub>1-x</sub>Zn<sub>x</sub>F<sub>4</sub> and Fe<sub>1-x</sub>Zn<sub>x</sub>F<sub>2</sub>
Binek, Christian
Kleeman, Wolfgang
Weak quasistatic singularities are evidenced within the Griffiths regime of temperatures Tc(x)≤T≤Tc(x=0) in the diluted antiferromagnet Fe1-xZnxF2, x=0.53, and in the diluted ferromagnet K2Cu1-xZnxF4, x=0.2, by measurements of the magnetic susceptibility, χ’ vs T, in zero external field. Significant deviations from classical (γ=1, for Fe0.47Zn0.53F2) and nonclassical (γ≳1, for K2Cu0.8Zn0.2F4) Curie-Weiss-type behavior, χ’∝[T-Tc(x)] -Y, are found just below Tc(x=0) by using linear-regression data analysis.
1995-05-01T07:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/5
https://digitalcommons.unl.edu/context/physicsbinek/article/1004/viewcontent/4_Evidence_of_dilution_induced_Griffiths_instabilities_in_K2Cu1_xZnxF4_and_Fe1_xZnxF2.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Physics
oai:digitalcommons.unl.edu:physicsbinek-1006
2017-03-26T11:01:22Z
publication:physicsfacpub
publication:physicsresearch
publication:physics
publication:physicsbinek
Magnetic-Field-Induced Griffiths Phase versus Random-Field Criticality and Domain Wall Susceptibility of Fe0.47Zn0.53F2
Binek, Christian
Kuttler, S.
Kleemann, Wolfgang
The well-known peak of the parallel ac susceptibility arising below TN in Fe0.47Zn0.53F2 splits into a narrow critical peak at Tc (H) and a broad field-induced Griffiths phase shoulder peaking at Tp>Tc(H) in magnetic fields H≳1.6 MA /m. Random-field (RF) criticality with α̃≈0 and subsequent rounding due to RF trapping of thermal fluctuations are observed upon zero-field cooling as T→Tc-(H). The frozen domain state obtained after rapid field cooling reveals excess susceptibility Δχw′∝H2.6, owing to rough walls with thermally activated stiffness.
1995-09-18T07:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/7
https://digitalcommons.unl.edu/context/physicsbinek/article/1006/viewcontent/6_Magnetic_Field_Induced_Griffiths_Phase_versus_Random_Field_Criticality_and_Domain_Wall_Susceptibility_of_Fe0.47Zn0.53F2.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Physics
oai:digitalcommons.unl.edu:physicsbinek-1008
2017-03-26T01:09:44Z
publication:physicsfacpub
publication:physicsresearch
publication:physics
publication:physicsbinek
Metamagnetic domains and dynamic fluctuations in FeBr<sub>2</sub>
Petracic, O.
Binek, Christian
Kleeman, Wolfgang
The mixed phase and the regime of non-critical fluctuations of the magnetic phase diagram of FeBr2 is investigated by SQUID susceptometry and light diffraction techniques. The experiments seem to evidence instability of the tricritical point as conjectured recently. The observation of stripe domains and light diffraction below and above Tm = 4.6 K and the virtual continuation of the phase transition line to above Tm are in agreement with the occurrence of a critical endpoint at Tm and of a bicritical endpoint at T > Tm. ©1997 American Institute of Physics.
1997-04-15T07:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/9
https://digitalcommons.unl.edu/context/physicsbinek/article/1008/viewcontent/8_Metamagnetic_domains_and_dynamic_fluctuations_in_FeBr2.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Physics
oai:digitalcommons.unl.edu:physicsbinek-1011
2006-09-13T20:13:49Z
publication:physicsfacpub
publication:physicsresearch
publication:physics
publication:physicsbinek
Density of Zeros on the Lee-Yang Circle Obtained from Magnetization Data of a Two-Dimensional Ising Ferromagnet
Binek, Christian
In order to provide experimental access to the statistical theory of Lee and Yang [Phys. Rev. 87, 410 (1952)] the density function g(θ) of zeros on the Lee-Yang circle has been determined for the first time by analyzing isothermal magnetization data m(H) of the Ising ferromagnet FeCl2 in axial magnetic fields H at temperatures 34≤T≤99 K. The validity of our approach is demonstrated by the perfect agreement of magnetic specific heat data as calculated from g(θ) and m(H) via Maxwell's relation. Moreover, the correct in-plane exchange constant of FeCl2 emerges from the series expansion of m(H) involved in the analysis.
1998-12-22T08:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/12
https://digitalcommons.unl.edu/context/physicsbinek/article/1011/viewcontent/11_Density_of_Zeros_on_the_Lee_Yang_Circle_Obtained_from_Magnetization_Data_of_a_Two_Dimensional_Ising_Ferromagnet.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Physics
oai:digitalcommons.unl.edu:physicsbinek-1010
2017-03-27T01:09:50Z
publication:physicsfacpub
publication:physicsresearch
publication:physics
publication:physicsbinek
Field-induced transverse spin ordering in FeBr<sub>2</sub>
Petracie, O.
Binek, Christian
Kleemann, Wolfgang
Neuhausen, U.
Lueken, H.
Weak first-order phase transitions from axial to oblique spin ordering in FeBr2 are evidenced by superconducting quantum interference device magnetometry in axial fields H1(T) above the multicritical point, Hm=2.4 MA/m, Tm=4.6 K, and below the antiferro-to-paramagnetic phase line, Hc (T), in agreement with recent specific-heat data [H. Aruga Katori, K. Katsumata, and M. Katori, Phys. Rev. B 54, R9620 (1996)]. The ordering of the in-plane moments is probably due to nondiagonal coupling to the longitudinal ones, both of which increase discontinuously at H1 (T) only under an additional symmetry-breaking transverse field.
1998-05-01T07:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/11
https://digitalcommons.unl.edu/context/physicsbinek/article/1010/viewcontent/10_Field_induced_transverse_spin_ordering_in_FeBr2.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Physics
oai:digitalcommons.unl.edu:physicsbinek-1013
2017-03-26T01:11:14Z
publication:physicsfacpub
publication:physicsresearch
publication:physics
publication:physicsbinek
Nonadiabatic heat-capacity measurements using a superconducting quantum interference device magnetometer
Kharkovski, A.I.
Binek, Christian
Kleeman, Wolfgang
Nonadiabatic measurements of the heat capacity involving sample-inherent thermometry are proposed. The method is realized with superconducting quantum interference device magnetometry and applied to FeBr2 single crystals by using the magnetization for both thermometry and relaxation calorimetry. When heating with a step pulse of laser light, the magnetization relaxes on a characteristic time scale Ί = RC, where C is the heat capacity and R is the heat resistance between the sample and the bath. R is independently determined from the temperature dependence of the magnetic moment measured with and without stationary light irradiation. ©2000 American Institute of Physics.
2000-10-09T07:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/14
https://digitalcommons.unl.edu/context/physicsbinek/article/1013/viewcontent/13_Nonadiabatic_heat_capacity_measurements_using_a_superconducting_quantum_interference_device_magnetometer.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Physics
oai:digitalcommons.unl.edu:physicsbinek-1012
2017-03-27T01:12:17Z
publication:physicsfacpub
publication:physicsresearch
publication:physics
publication:physicsbinek
Neutron scattering study of transverse magnetism
Binek, Christian
Kato, T.
Kleemann, Wolfgang
Petracic, O.
Bertrand, D.
Bourdarot, F.
Burlet, P.
Katori, H. Aruga
Katsumata, K.
Prokes, K.
Welzel, S.
In order to clarify the nature of the additional phase transition at H1 (T) < Hc (T) of the layered antiferromagnetic (AF) insulator FeBr2 as found by Aruga Katori et al. (1996) we measured the intensity of different Bragg-peaks in different scattering geometries. Transverse AF ordering is observed in both AF phases, AFI and AFII. Its order parameter exhibits a peak at T1 = T (H1) in temperature scans and does not vanish in zero field. Possible origins of the step-like increase of the transverse ferromagnetic ordering induced by a weak in-plane field component when entering AFI below T1 are discussed.
1996-12-06T08:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/13
https://digitalcommons.unl.edu/context/physicsbinek/article/1012/viewcontent/12_Neutron_scattering_study_of_transverse_magnetism.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Physics
oai:digitalcommons.unl.edu:physicsbinek-1015
2017-03-26T11:10:18Z
publication:physicsfacpub
publication:physicsresearch
publication:physics
publication:physicsbinek
Magnetic phase diagram of the diluted metamagnet Fe<sub>0.95</sub>Mg<sub>0.05</sub>Br<sub>2</sub>
Katori, H. Aruga
Katsumata, K.
Petracic, O.
Kleemann, Wolfgang
Kato, T.
Binek, Christian
The axial magnetic phase diagram of the antiferromagnet Fe0.95Mg0.05Br2 is studied by specific heat, superconducting quantum interference device, and Faraday rotation techniques. The diamagnetic impurities give rise to random-field criticality along the second-order phase line Hc(T) between TN=13.1 K and a multicritical point at Tm≈5 K, and to a spin-flop line between Tm and the critical end-point temperature Te≈3.5 K. The phase line H1(T)c(T) ending at Tm is probably due to symmetric nondiagonal exchange.
2001-03-14T08:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/16
https://digitalcommons.unl.edu/context/physicsbinek/article/1015/viewcontent/15_Magnetic_phase_diagram_of_the_diluted_metamagnet_Fe0.95Mg0.05Br2.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Physics
oai:digitalcommons.unl.edu:physicsbinek-1014
2006-09-14T16:43:18Z
publication:physicsfacpub
publication:physicsresearch
publication:physics
publication:physicsbinek
Interacting ferromagnetic nanoparticles in discontinuous Co<sub>80</sub>Fe<sub>20</sub>/Al<sub>2</sub>O<sub>3</sub> multilayers: From superspin glass to reentrant superferromagnetism
Kleeman, W.
Petracic, O.
Binek, Christian
Kakazei, G.N.
Pogorelov, Yu. G.
Sousa, J.B.
Cardoso de Freitas, Susana
Freitas, P.P.
Dipolar superferromagnetism with reentrant low-temperature superspin glass behavior is observed on a randomly distributed ferromagnetic nanoparticle systems in discontinuous metal-insulator multilayers [Co80Fe20/Al2O3 (3 nm)] 10 with nominal thickness 1.1<~t<~1.3 nm by use of ac susceptometry and dc magnetometry. At t=1.0 nm, superspin glass-like freezing is evidenced by the criticality of dynamic and nonlinear susceptibilities.
2001-03-12T08:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/15
https://digitalcommons.unl.edu/context/physicsbinek/article/1014/viewcontent/14_Interacting_ferromagnetic_nanoparticles_in_discontinuous_Co80Fe20ÕAl2O3_multilayers.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Physics
oai:digitalcommons.unl.edu:physicsbinek-1016
2017-03-25T23:20:59Z
publication:physicsfacpub
publication:physicsresearch
publication:physics
publication:physicsbinek
Off-diagonal exchange-induced transverse and field-induced spin-flop order in the diluted metamagnet Fe<sub>0.85</sub>Mg<sub>0.15</sub>Br<sub>2</sub>
Kleeman, Wolfgang
Katori, H. Aruga
Kato, T.
Binek, Christian
Katsumata, K.
Specific heat and Faraday rotation magnetometry were used to determine the axial magnetic phase diagram of the dilute hexagonal antiferromagnet Fe0.85Mg0.15Br2. In contrast to metamagnetic pure FeBr2, the first-order line of transverse phase transitions, H1(T), is disconnected with the antiferro-to-paramagnetic phase line Hc(T) and extends down to Ht=0 at Tt≈8.7 . This is attributed to symmetric off-diagonal exchange in the presence of structural disorder. Moreover, a spin-flop phase emerges beyond Hc(T) up to a bicritical point (Tb≈9.3 , μoHb≈1.3 ).
2001-09-01T07:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/17
https://digitalcommons.unl.edu/context/physicsbinek/article/1016/viewcontent/16_Off_diagonal_exchange_induced_transverse_and.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Physics
oai:digitalcommons.unl.edu:physicsbinek-1017
2006-09-14T17:34:26Z
publication:physicsfacpub
publication:physicsresearch
publication:physics
publication:physicsbinek
Dilution-induced enhancement of the blocking temperature in exchange-bias heterosystems
Chen, Xi
Binek, Christian
Hochstrat, A.
Kleemann, Wolfgang
The temperature dependence of the exchange bias field is investigated by superconducting quantum interference device magnetometry in Fe1-xZnxF2(110)/Fe14 nm/Ag35 nm, x=0.4. Its blocking temperature exhibits a significant enhancement with respect to the global ordering temperature TN=46.9 K, of the bulk antiferromagnet Fe0.6Zn0.4F2. The enhancement is attributed to fluctuations of the diamagnetic dilution which creates clusters on all length scales having a Zn dilution of 0<~x<~1. While the infinite clusters give rise to the well-known Griffiths phase, finite clusters also provoke a local enhancement of the exchange bias. The temperature dependence of the integral exchange bias effect is modeled by averaging all local contributions of the antiferromagnetic surface magnetization which exhibit a surface critical behavior.
2001-12-13T08:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/18
https://digitalcommons.unl.edu/context/physicsbinek/article/1017/viewcontent/18_Dilution_induced_enhancement_of_the_blocking_temperature_in_exchange_bias_heterosystems.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Physics
oai:digitalcommons.unl.edu:physicsbinek-1018
2017-03-26T11:03:26Z
publication:physicsfacpub
publication:physicsresearch
publication:physics
publication:physicsbinek
Superspin-glass nature of discontinuous Co<sub>80</sub>Fe<sub>20</sub>/Al<sub>2</sub>O<sub>3</sub> multilayers
Sahoo, Sarbeswar
Petracic, O.
Binek, Christian
Kleemann, Wolfgang
Sousa, J.B.
Cardoso de Freitas, Susana
Freitas, P.P.
Ferromagnetic single domain particles of CoFe in discontinuous magnetic multilayers [Co80Fe20 (0.9 nm)/ Al2O3(3 nm)] 10 reveal spin-glass ordering below Tg=43.6 K as evidenced by the criticality of the nonlinear susceptibility. Dynamic critical scaling yields exponents zν=8.0 and β=1.0 in both zero and weak applied field, where an Almeida-Thouless line is encountered. In fields exceeding 2 mT a crossover into a chiral glass regime seems to occur.
2002-03-13T08:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/19
https://digitalcommons.unl.edu/context/physicsbinek/article/1018/viewcontent/19_Superspin_glass_nature_of_discontinuous_Co80Fe20Al2O3_multilayers.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Physics
oai:digitalcommons.unl.edu:physicsbinek-1020
2017-03-27T01:14:02Z
publication:physicsfacpub
publication:physicsresearch
publication:physics
publication:physicsbinek
Training of the exchange-bias effect in NiO-Fe heterostructures
Hochstrat, A.
Binek, Christian
Kleemann, Wolfgang
The training effect of a NiO(001)/Fe(110) heterostructure is studied from magnetic hysteresis loops measured by superconducting quantum interference device magnetometry. Consecutive hysteresis loops exhibit a decreasing exchange bias effect. This behavior is known as the training effect, which reflects the dependence of the exchange bias field on the antiferromagnetic interface magnetization. In order to evidence this dependence, we study the decrease of the total saturation magnetization of the heterostructure for an increasing number of hysteresis cycles. Assuming proportionality between the interface magnetization and the total saturation magnetization, the description of the data is consistent within the phenomenological Meiklejohn Bean approach.
2002-09-30T07:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/21
https://digitalcommons.unl.edu/context/physicsbinek/article/1020/viewcontent/21_Training_of_the_exchange_bias_effect_in_NiO_Fe_heterostructures.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Physics
oai:digitalcommons.unl.edu:physicsbinek-1021
2017-03-26T12:09:45Z
publication:physicsfacpub
publication:physicsresearch
publication:physics
publication:physicsbinek
Giant metamagnetic moments in a granular FeCl<sub>2</sub>-Fe heterostructure
Sahoo, Sarbeswar
Binek, Christian
Kleemann, Wolfgang
Giant moments are observed at low temperatures in a granular FeCl2-Fe heterostructure owing to a local metamagnetic transformation of the antiferromagnetic (AF) FeCl2 matrix due to dipolar interactions. A model of metamagnetically (MM) "dressed" single-domain Fe particles is suggested to explain the observations. These include polydispersive ac susceptibility induced by AF-MM domain configurations and weak exchange bias due to non-spin-flipped AF crystallites.
2003-11-25T08:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/22
https://digitalcommons.unl.edu/context/physicsbinek/article/1021/viewcontent/22_Giant_metamagnetic_moments_in_a_granular_FeCl2_Fe_heterostructure.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Physics
oai:digitalcommons.unl.edu:physicsbinek-1019
2017-03-25T23:37:55Z
publication:physicsfacpub
publication:physicsresearch
publication:physics
publication:physicsbinek
Domain Wall Relaxation, Creep, Sliding, and Switching in Superferromagnetic Discontinuous Co<sub>80</sub>Fe<sub>20</sub>/Al<sub>2</sub>O<sub>3</sub> Multilayers
Chen, X.
Sichelschmidt, O.
Kleemann, Wolfgang
Binek, Christian
Sousa, J.B.
Cardoso de Freitas, Susana
Freitas, P.P.
The ac susceptibility of a superferromagnetic discontinuous multilayer [Co80Fe20(1.4 nm)/ Al2O3(3 nm)]10 is measured as a function of temperature, frequency, and field amplitude and compared to static and dynamic hysteresis loops. Its properties are successfully mapped onto the predicted [T. Nattermann, V. Pokrovsky, and V. M. Vinokur, Phys. Rev. Lett. 87, 197005 (2001).] dynamical phase transitions, which link the relaxation, creep, sliding, and switching regimes of pinned domain walls.
2002-09-23T07:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/20
https://digitalcommons.unl.edu/context/physicsbinek/article/1019/viewcontent/20_Domain_Wall_Relaxation__Creep__Sliding__and_Switching_in_Superferromagnetic_Discontinuous_Co80Fe20Al2O3_Multilayers.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Physics
oai:digitalcommons.unl.edu:physicsbinek-1023
2017-03-30T11:06:49Z
publication:physicsfacpub
publication:mrsecfacpubs
publication:physicsresearch
publication:physics
publication:physicsbinek
publication:materialsresearchscieeng
Perpendicular exchange bias and its control by magnetic, stress and electric fields
Binek, Christian
Borisov, Pavel
Chen, Xi
Sahoo, S.
Kleemann, Wolfman
erpendicular exchange bias (PEB) involving perpendicular magnetic anisotropy (PMA) in both the antiferromagnetic (AF) pinning and the ferromagnetic (FM) sensor layer is expected to become important in future perpendicular recording and sensing devices. Further, because of the reduced spin dimensionality, PEB promises to be easier understandable than the conventional planar exchange bias (EB). In addition to its first realization using the Ising-type AF compounds FeF2 and FeCl2 we have tested control strategies of EB being alternative to the conventional magnetic and thermal ones. Indeed, specific symmetry properties of the pinning layer have been shown to enable mechanical (viz. piezomagnetic via FeF2) and electric control (viz. magneto-electric via Cr2O3) of EB, respectively. Electric control promises to become relevant for TMR devices in MRAM technology.
2005-03-08T08:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/24
https://digitalcommons.unl.edu/context/physicsbinek/article/1023/viewcontent/24_Perpendicular_exchange_bias_and_its_control_by_magnetic__stress.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Physics
oai:digitalcommons.unl.edu:physicsbinek-1022
2006-09-14T18:11:14Z
publication:physicsfacpub
publication:physicsresearch
publication:physics
publication:physicsbinek
Training of the exchange-bias effect: A simple analytic approach
Binek, Christian
raining of the exchange bias effect in antiferro-/ferromagnetic heterostructures is considered in the theoretical framework of spin configurational relaxation, which is activated through consecutively cycled hysteresis loops. The corresponding exchange bias fields, µ0 HEB(n), reveal relaxation from the initial state, n = 1, of high antiferromagnetic interface magnetization to the equilibrium state of reduced magnetization in the limit of large n. The evolution of µ0HEB vs n is calculated with the help of a discretized Landau-Khalatnikov equation, where the continuous time parameter is replaced by the loop index n. The result reveals the origin of the well established but hitherto unexplained power-law decay of µ0HEB(n) for n > 1. Moreover, in contrast with the breakdown of the power-law behavior at n = 1, the relaxation approach describes the training effect for n≥1. The full capability of the theory is explored in comparison with experimental results obtained recently on a NiO(001)/Fe(110) heterostructure.
2004-07-20T07:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/23
https://digitalcommons.unl.edu/context/physicsbinek/article/1022/viewcontent/23_Training_of_the_exchange_bias_effect_A_simple_analytic_approach.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Physics
oai:digitalcommons.unl.edu:physicsbinek-1024
2017-03-30T11:08:33Z
publication:physicsfacpub
publication:mrsecfacpubs
publication:physicsresearch
publication:physics
publication:physicsbinek
publication:materialsresearchscieeng
Electrically controlled exchange bias for spintronic applications
Binek, Christian
Hochstrat, A.
Chen, X.
Borisov, Pavel
Kleemann, Wolfman
Doudin, Bernard
Exchange coupling between a magnetoelectric (111)-oriented Cr2O3 single crystal and a CoPt multilayer with perpendicular anisotropy exhibits an exchange bias field proportional to the applied axial electric field. Extrapolation from bulk to thin film magnetoelectric pinning system suggests promising spintronic applications due to coupling between the electric field-controlled magnetization and the magnetization of a neighbor ferromagnetic layer. Pure voltage control of magnetic configurations of tunneling magnetoresistance spin valves is an attractive alternative to current-induced magnetization switching. ©2005 American Institute of Physics
2005-05-04T07:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/25
https://digitalcommons.unl.edu/context/physicsbinek/article/1024/viewcontent/25_Electrically_controlled_exchange_bias_for_spintronic_applications.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Physics
oai:digitalcommons.unl.edu:physicsbinek-1025
2017-03-26T12:02:36Z
publication:physicsfacpub
publication:physicsresearch
publication:physics
publication:physicsbinek
Magnetic states of granular layered CoFe-Al<sub>2</sub>O<sub>3</sub>
Sousa, J.B.
Kakazei, G.N.
Pogorelov, Y.G.
Santos, J.A.M.
Petracic, O.
Kleemann, Wolfgang
Binek, Christian
Cardoso de Freitas, Susana
Freitas, P.P.
Pereira de Azevedo, M.M.
Lesnik, N.A.
Rokhlin, Stanislav
Wigen, P.E.
The granular layered magnetic system Co80Fe20(t)/Al2 O3 (3 nm), where the Co80Fe20 layers of nominal thickness t form separate, almost spherical magnetic granules of typical diameter 2-3 nm between the Al2O3 spacers, was studied. We discuss measurements of the dc and ac magnetic susceptibility χ for 1 nm
2001-07-04T07:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/26
https://digitalcommons.unl.edu/context/physicsbinek/article/1025/viewcontent/26.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Physics
oai:digitalcommons.unl.edu:physicsbinek-1026
2006-09-22T17:58:54Z
publication:physicsfacpub
publication:mrsecfacpubs
publication:physicsresearch
publication:physics
publication:physicsbinek
publication:materialsresearchscieeng
Reversible hysteresis loop tuning
Berger, Andreas
Binek, Christian
Margulies, D. T.
Moser, A.
Fullerton, E. E.
We utilize antiferromagnetically coupled bilayer structures to magnetically tune hysteresis loop properties. Key element of this approach is the non-overlapping switching fi eld distribution of the two magnetic layers that make up the system: a hard magnetic CoPtCrB layer (HL) and a soft magnetic CoCr layer (SL). Both layers are coupled antiferromagnetically through an only 0.6-nm-thick Ru interlayer. The nonoverlapping switching fi eld distribution allows the measurement of magnetization reversal in the SL at low fi elds while keeping the magnetization state of the HL unperturbed. Applying an appropriate high fi eld or high fi eld sequence changes the magnetic state of the HL, which then infl uences the SL magnetization reversal due to the interlayer coupling. In this way, the position and shape of the SL hysteresis loop can be changed or tuned in a fully reversible and highly effective manner. Here, we study specifi cally how the SL hysteresis loop characteristics change as we move the HL through an entire high fi eld hysteresis loop sequence.
2005-11-28T08:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/27
https://digitalcommons.unl.edu/context/physicsbinek/article/1026/viewcontent/reversible_hysteresis_for_Commons.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Hysteresis
Hysteresis tuning
AFC media
Magnetic thin fi lms
Physics
oai:digitalcommons.unl.edu:physicsbinek-1027
2017-03-21T16:17:12Z
publication:physicsfacpub
publication:mrsecfacpubs
publication:physicsresearch
publication:physics
publication:physicsbinek
publication:materialsresearchscieeng
Magnetoelectronics with magnetoelectrics
Binek, Christian
Doudin, Bernard
Magnetoelectric films are proposed as key components for spintronic applications. The net magnetic moment created by an electric field in a magnetoelectric thin film influences the magnetization state of a neighbouring ferromagnetic layer through exchange coupling. Pure electrical control of magnetic confi gurations of giant magnetoresistance spin valves and tunnelling magnetoresistance elements is therefore achievable. Estimates based on documented magnetoelectric tensor values show that exchange fields reaching 100 mT can be obtained. We propose a mechanism alternative to current-induced magnetization switching, providing access to a wide range of device impedance values and opening the possibility of simple logic functions.
2004-12-20T08:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/28
https://digitalcommons.unl.edu/context/physicsbinek/article/1027/viewcontent/Magnetoelectronics_for_Commons.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Physics
oai:digitalcommons.unl.edu:physicsbinek-1028
2008-02-14T21:39:16Z
publication:physicsfacpub
publication:mrsecfacpubs
publication:physicsresearch
publication:physics
publication:physicsbinek
publication:materialsresearchscieeng
Dynamic enhancement of the exchange bias training effect
Sahoo, Sarbeswar
Polisetty, Srinivas
Binek, Christian
Berger, Andreas
Exchange bias in coupled magnetic thin films and its accompanying training effect are fundamental interface phenomena with significant impact in spintronic applications. Both effects are well known in heterosystems of ferro- and antiferromagnetic thin films. Here, we report on the dynamic enhancement of the training effect in an exchange coupled bilayer of soft and hard ferromagnetic materials. Training is referred to as a gradual change of the bias field, which evolves upon cycling the soft layer through consecutive hysteresis loops. Its dynamic enhancement is observed with increasing sweep rate of the applied magnetic field from quasistatic to the fully dynamic range. A dynamically generalized theory based on triggered relaxation is in excellent agreement with the training data. Additionally, we evidence the remarkable universality of our theoretical approach when applying it to the dynamically altered training effect of a conventional exchange bias system involving an antiferromagnetic pinning layer.
2007-03-16T07:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/29
https://digitalcommons.unl.edu/context/physicsbinek/article/1028/viewcontent/JApplPhys_101_053902.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
exchange bias
training effect
dynamic hysteresis
Physics
oai:digitalcommons.unl.edu:physicsbinek-1029
2007-03-27T17:53:02Z
publication:physicsfacpub
publication:mrsecfacpubs
publication:physicsresearch
publication:physics
publication:physicsbinek
publication:materialsresearchscieeng
Piezomagnetism in epitaxial Cr2O3 thin films and spintronic applications
Sahoo, Sarbeswar
Binek, Christian
Stress-induced perturbation of the antiferromagnetic long-range order in epitaxially grown Cr2O3 thin films gives rise to pronounced piezomagnetism and a significant reduction of the antiferromagnetic ordering temperature. The temperature dependence of the piezomagnetic moment measured by superconducting quantum interference device magnetometry reveals a power law behaviour with a critical exponent 2B=0.66 in accordance with the Ising anisotropy of a three-dimensional system. The observed shift of the Neel temperature allows estimating the internal lateral stress which is in excellent agreement with an independent estimate based on the elastic properties of Cr2O3 and the lattice mismatch at the interface between the sapphire substrate and the isostructural (111) Cr2O3 thin film. The isothermal freezing field dependence of the piezomoment is interpreted in terms of Zeeman energy arguments. Implications of the piezomagnetic effects for spintronic devices and the investigation of the piezomagnetoelectric effect are briefly discussed.
2007-03-27T07:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/58
https://digitalcommons.unl.edu/context/physicsbinek/article/1029/viewcontent/PiezomagnetismPML.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Piezomagnetism
spintronics
exchange bias
thin films
magnetoelectric effect
Physics
oai:digitalcommons.unl.edu:physicsbinek-1031
2017-03-26T11:05:11Z
publication:physicsfacpub
publication:physicsresearch
publication:physics
publication:physicsbinek
Cole-Cole Analysis of the Superspin Glass System Co<sub>80</sub>Fe<sub>20</sub>/Al<sub>2</sub>O<sub>3</sub>
Petracic, O.
Sahoo, Sarbeswar
Binek, Christian
Kleemann, Wolfgang
Sousa, J.B.
Cardoso de Freitas, Susana
Freitas, P.P.
Ac susceptibility measurements were performed on discontinuous magnetic multi-layers [Co80Fe20 (t)/Al2O3 (3 nm)] 10, t = 0.9 and 1.0 nm, by Superconducting Quantum Interference Device (SQUID) magnetometry. The CoFe forms nearly spherical ferromagnetic single-domain nanoparticles in the diamagnetic Al2O3 matrix. Due to dipolar interactions and random distribution of anisotropy axes the system exhibits a spin-glass phase. We measured the ac susceptibility as a function of temperature 20 ≤ T ≤ 100 K at different dc fi elds and as a function of frequency 0.01 ≤ f ≤ 1000 Hz. The spectral data were successfully analyzed by use of the phenomenological Cole–Cole model, giving a power-law temperature dependence of the characteristic relaxation time τc and a high value for the polydispersivity exponent, α ≈ 0.8, typical of spin glass systems.
2003-04-09T07:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/31
https://digitalcommons.unl.edu/context/physicsbinek/article/1031/viewcontent/Binek_PT_2003__Cole_Cole_Analysis.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Physics
oai:digitalcommons.unl.edu:physicsbinek-1032
2017-03-26T12:04:24Z
publication:physicsfacpub
publication:physicsresearch
publication:physics
publication:physicsbinek
Magneto-Thermal Behavior of a Granular FeCl<sub>2</sub>–Fe Heterostructure
Sahoo, Sarbeswar
Binek, Christian
Kleemann, Wolfgang
A granular system consisting of ferromagnetic single-domain Fe particles in an antiferromagnetic FeCl2 matrix was prepared by coevaporation in an ultra-high vacuum environment. The structural and magnetic properties were investigated by X-ray diffractometry and superconducting quantum interference device magnetometry, respectively. The heterostructure combines the properties of superparamagnetic Fe granules and the antiferromagnetism of the FeCl2 matrix. In addition, dipolar interaction-induced giant moments are observed below the Néel temperature of the FeCl2 matrix. The thermomagnetic properties of the giant moments are studied.
2004-01-01T08:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/32
https://digitalcommons.unl.edu/context/physicsbinek/article/1032/viewcontent/Binek_PT_2004_Magneto__DC_version.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Granular thin films; Dipolar interactions; Exchange coupling
Physics
oai:digitalcommons.unl.edu:physicsbinek-1033
2017-02-24T02:16:42Z
publication:physicsfacpub
publication:mrsecfacpubs
publication:physicstsymbal
publication:physicsresearch
publication:physics
publication:physicsbinek
publication:materialsresearchscieeng
publication:physicsjaswal
Ferroelectric control of magnetism in BaTiO3 /Fe heterostructures via interface strain coupling
Sahoo, Sarbeswar
Polisetty, Srinivas
Duan, Chun-Gang
Jaswal, Sitaram S.
Tsymbal, Evgeny Y.
Binek, Christian
Reversible control of magnetism is reported for a Fe thin film in proximity of a BaTiO3 single crystal. Large magnetization changes emerge in response to ferroelectric switching and structural transitions of BaTiO3 controlled by applied electric fields and temperature, respectively. Interface strain coupling is the primary mechanism altering the induced magnetic anisotropy. As a result, coercivity changes up to 120% occur between the various structural states of BaTiO3. Up to 20% coercivity change is achieved via electrical control at room temperature. Our all solid state ferroelectric-ferromagnetic heterostructures open viable possibilities for technological applications.
2007-10-30T07:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/57
https://digitalcommons.unl.edu/context/physicsbinek/article/1033/viewcontent/GetPDFServlet.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Physics
oai:digitalcommons.unl.edu:physicsbinek-1034
2017-04-11T18:31:06Z
publication:physicsfacpub
publication:mrsecfacpubs
publication:physicsresearch
publication:physicsbelashchenko
publication:physics
publication:physicsbinek
publication:materialsresearchscieeng
Isothermal low-field tuning of exchange bias in epitaxial Fe/Cr2O3/Fe
Sahoo, Sarbeswar
Mukherjee, Tathagata
Belashchenko, Kirill D.
Binek, Christian
Moderate dc magnetic fields of less than 1 T allow tuning the exchange bias in an epitaxially grown Fe 10 nm/Cr2O3 2.7 nm/Fe 10 nm trilayer between negative and positive bias fields. Remarkably, this tunable exchange bias is observed at least up to 395 K which exceeds the Néel temperature of bulk Cr2O3 (307 K). The presence of spontaneous exchange bias and the absence of training effects at room temperature suggest the existence of stable interface moments independent of antiferromagnetic long range order in Cr2O3. Furthermore, the coercivity remains constant, independent of the exchange bias field. In contrast, large training associated with nonequilibrium spin configurations of antiferromagnetically ordered Cr2O3 appears below 50 K.
2007-10-30T07:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/33
https://digitalcommons.unl.edu/context/physicsbinek/article/1034/viewcontent/Sahoo_APL_91_172506_2007.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
exchange bias
Physics
oai:digitalcommons.unl.edu:physicsbinek-1035
2017-03-26T12:08:14Z
publication:physicsfacpub
publication:physicsresearch
publication:physics
publication:physicsbinek
Yang-Lee edge singularities determined from experimental high-field magnetization data
Binek, Christian
Kleemann, Wolfgang
Aruga Katori, H.
The isothermal magnetization m (H) of the metamagnet FeCl2 is measured in axial magnetic fields 0 ≤ μ0Ha ≤ 12 T at temperatures 34 ≤ T ≤ 53 K above the Néel temperature, where the system is essentially a two-dimensional Ising ferromagnet. The analysis of the data indicates experimental accessibility of the critical exponent μ of the Yang-Lee edge singularities. They manifest themselves in divergences of the density functions g(θ), which quantify the distribution of the zeros of the partition function on the Lee-Yang unit circle in the complex plane. In accordance with the hypothesis of universality, a critical exponent close to the theoretical prediction for the two-dimensional Ising ferromagnet, μ = –1/6, is found.
2001-08-01T07:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/34
https://digitalcommons.unl.edu/context/physicsbinek/article/1035/viewcontent/Binek_JPCM_2001_Yang_Lee__DC_VERSION.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Physics
oai:digitalcommons.unl.edu:physicsbinek-1036
2017-03-26T11:07:01Z
publication:physicsfacpub
publication:physicsresearch
publication:physics
publication:physicsbinek
Magnetic relaxation phenomena in the superspin-glass system [Co<sub>80</sub>Fe<sub>20</sub>/Al<sub>2</sub>O<sub>3</sub>]<sub>10</sub>
Sahoo, Sarbeswar
Petracic, O.
Binek, Christian
Kleemann, Wolfgang
Sousa, J. B.
Cardoso de Freitas, Susana
Freitas, P. P.
Relaxation and temperature cycles of thermoremanent magnetization, MTRM, in the superspin-glass phase of [Co80Fe20 (0.9 nm)/Al2O3 (3 nm)] 10 have been investigated. The relaxation of MTRM exhibits ageing phenomena. In negative temperature cycles for temperature steps larger than 1 K the magnetic state is retrieved (memory effect) on returning to the measurement temperature. This property is independent of the application of a field step during intermediate cooling. In positive temperature cycles the relaxation is suppressed after temporary heating. The observations are discussed in the light of both the droplet and the hierarchical picture.
2002-11-01T08:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/35
https://digitalcommons.unl.edu/context/physicsbinek/article/1036/viewcontent/Binek_JPCM_2002_Magnetic_relaxation__DC_VERSION.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Physics
oai:digitalcommons.unl.edu:physicsbinek-1044
2007-12-07T18:21:16Z
publication:physicsfacpub
publication:physicsresearch
publication:physics
publication:physicsbinek
Ac susceptibility studies of discontinuous Co80Fe20Al2O3 multilayers
Binek, Christian
Discontinuous metal–insulator multilayers [Co80Fe20(t)/Al2O3(3 nm)]10 are prepared by ion-beam sputtering and investigated by SQUID magnetometry and previous AC susceptometry. For 1.0less-than-or-equals, slanttless-than-or-equals, slant1.6 nm, two coexisting subsystems of dipolar coupled nanoparticles are encountered. While a spin-glass-like freezing particulate fraction dominates at t=1.0 nm, a percolating dipolar ferromagnetic fraction becomes increasingly important at higher nominal thickness of t.
2001-11-14T08:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/43
https://digitalcommons.unl.edu/context/physicsbinek/article/1044/viewcontent/AC_Susceptibility_studies_of_discontinuous_Co80Fe20_Al2O3_Multilayers.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Ac
susceptibility
Co80Fe20Al2O3
multilayers
Physics
oai:digitalcommons.unl.edu:physicsbinek-1045
2007-12-07T18:25:35Z
publication:physicsfacpub
publication:physicsresearch
publication:physics
publication:physicsbinek
Freezing field dependance of the exchange bias in uniaxial FeF2-CoPt heterosystems with perpendicular anisotropy
Binek, Christian
The exchange bias effect is measured for the first time in FeF2–CoPt heterosystems with perpendicular anisotropy. The exchange previous field exhibits a strong dependence on the axial previous freezing field. This behavior is explained in terms of the microscopic spin structure at the interface, which is established on cooling to below TN. We calculate the dependence of the spin structure on the previous freezing field within the framework of an Ising model. It takes into account the Zeeman energy as well as an antiferromagnetic exchange coupling between the adjacent layers at the interface.
2000-07-13T07:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/44
https://digitalcommons.unl.edu/context/physicsbinek/article/1045/viewcontent/Freezing_field_dependence_of_the_exchange_bias_in_uniaxial_FeF2_CoPt_Heterosystems_with_perpendicular_antisotropy.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Freezing
field
exchange bias
uniaxial
perpendicular
anisotropy
Physics
oai:digitalcommons.unl.edu:physicsbinek-1043
2007-12-07T18:13:48Z
publication:physicsfacpub
publication:physicsresearch
publication:physics
publication:physicsbinek
Exchange Bias in FeF20-CoPt heterosystems with perpendicular anisotropy
Binek, Christian
The previous exchange bias effect is measured in heterosystems with perpendicular anisotropy consisting of Co/Pt multilayers on top of the (0 0 1) face of a previous FeF2 single crystal. The resulting previous exchange field HE exhibits a strong dependence on temperature and the axial freezing field, HF. Within the framework of an Ising-type model, the HE vs. T as well as the HE vs. HF data are explained in terms of the microscopic spin structure at the interface.
2001-11-14T08:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/42
https://digitalcommons.unl.edu/context/physicsbinek/article/1043/viewcontent/Exchange_Bias_in_FeF2_Co_Pt_Heterosystems_with_perpendicular_antisotropy.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Exchange
Bias
FeF20-CoPt
Heterosystems
perpendicular
anisotropy
Exchange Bias
Fef2-CoPt Heterosystems
Perpendicular anisotropy
Physics
oai:digitalcommons.unl.edu:physicsbinek-1037
2007-12-07T17:28:54Z
publication:physicsfacpub
publication:physicsresearch
publication:physics
publication:physicsbinek
Extrinsic control of the exchange bias
Binek, Christian
A new control mechanism for the exchange bias effect in magnetic heterostructures is proposed. It takes advantage of the magnetoelectric effect which takes place in the antiferromagnetic pinning layer. In contrast with the pioneering AC measurements of the magnetoelectric effect, we investigate the magnetic response of the prototypical magnetoelectric compound Cr2O3 on static electric fields. The linear dependence of the magnetic moment on the applied axial electric field and the temperature dependence of the corresponding slopes αshort parallel are measured by DC SQUID magnetometry. The contribution of the field-induced surface magnetization and its impact on the exchange bias effect is estimated.
2004-01-04T08:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/36
https://digitalcommons.unl.edu/context/physicsbinek/article/1037/viewcontent/Extrinsic_Control_of_the_Exchange_Bias.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Extrinsic
Control
Exchange
Bias
Extrinsic Control
Exchange Bias
Physics
oai:digitalcommons.unl.edu:physicsbinek-1038
2007-12-07T17:35:15Z
publication:physicsfacpub
publication:physicsresearch
publication:physics
publication:physicsbinek
Superferromagnetic domain state dynamics in discontinuous CoFe/Al2O3
Binek, Christian
Magnetization hysteresis and AC susceptibility measurements were performed on the discontinuous metal–insulator multilayer [Co80Fe20(1.4 nm)/Al2O3(3 nm)]10. CoFe forms ferromagnetic single-previous domain term particles being embedded in the Al2O3 matrix. Due to strong dipolar inter-particle interactions a “previous superferromagnetic term” correlation of particle moments was previously stated. The dynamical magnetic properties of the superferromagnet can be understood in the framework of previous domain term wall motion in an impure ferromagnet. Kinetic simulations are employed, which are based on field and temperature-dependent previous domain term wall velocities. The magnetization hysteresis as well as the AC susceptibility, χ′−iχ′′, are calculated and compared to our experimental results and yield a good agreement. The analysis of the Cole–Cole plots, χ′′ vs. χ′, is particularly interesting. They are shown to serve as fingerprints for the different dynamic behavior as claimed previously.
2004-01-08T08:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/37
https://digitalcommons.unl.edu/context/physicsbinek/article/1038/viewcontent/Superferromagnetic_domain_state_dynamics_in_discontinuous_CoFe_Al203.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Superferromagnetic
domain
state
dynamics
discontinuous
CoFe/Al2O3
domain state
Physics
oai:digitalcommons.unl.edu:physicsbinek-1041
2007-12-07T17:54:42Z
publication:physicsfacpub
publication:physicsresearch
publication:physics
publication:physicsbinek
Exchange Bias in a generalized Meiklejohn-Bean approach
Binek, Christian
A generalized Meiklejohn–Bean model is considered in order to derive an analytic expression for the dependence of the previous exchange bias term field on the layer thickness involved in ferromagnetic/antiferromagnetic heterosystems, on the orientation of the applied magnetic field with respect to the magnetic easy axes and on the quenched magnetization MAF of the antiferromagnetic pinning layer. While MAF is a well-known feature of field-cooled dilute antiferromagnets, it seems to occur quite generally also in pure AF pinning substrates. The new analytic expressions are successfully compared with recent experimental results and Monte Carlo investigations.
2001-08-15T07:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/40
https://digitalcommons.unl.edu/context/physicsbinek/article/1041/viewcontent/Exchange_Bias_in_a_generalized_Meiklejohn_Bean_Approach.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Exchange
Bias
generalized
Meiklejohn
Bean
Approach
Exchange Bias
Meiklejohn-Bean
Physics
oai:digitalcommons.unl.edu:physicsbinek-1039
2007-12-07T17:42:58Z
publication:physicsfacpub
publication:physicsresearch
publication:physics
publication:physicsbinek
Magnetic states of discontinuous Co80Fe20Al2O3 Multilayers
Binek, Christian
Discontinuous metal–insulator multilayers [Co80Fe20(t)/Al2O3(3 nm)]n were studied by SQUID magnetometry and AC susceptometry. CoFe forms ferromagnetic particles in the Al2O3 matrix. In this paper, we focus on the field dependence of the AC susceptibility of samples with t=1.3 nm. We find strong evidence for transitions from a superpara- to a superferromagnetic and, finally, to a reentrant superspin glass previous state.
2001-10-24T07:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/38
https://digitalcommons.unl.edu/context/physicsbinek/article/1039/viewcontent/Magnetic_states_of_discontinuous_Co80Fe20_Al2O3_Multilayers.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Magnetic
states
discontinuous
Co80Fe20Al2O3
Multilayers
Magnetic States
Co80Fe20Al203 Multilayers
Physics
oai:digitalcommons.unl.edu:physicsbinek-1040
2007-12-07T17:50:39Z
publication:physicsfacpub
publication:physicsresearch
publication:physics
publication:physicsbinek
Exchange Bias in Fe0.6Zn0.4F2 Heterostructures
Binek, Christian
The previous exchange bias field, He, is measured in Fe0.6Zn0.4F2/Fe heterosystems prepared from Fe layers of 14 and 5 nm thickness which are deposited on top of the compensated (1 1 0) surface of the antiferromagnet. Deviations from a linear dependence of He on the magnetization of the Fe layer are attributed to ferromagnetic domains. Moreover, piezomagnetism and its influence on He are evidenced.
2001-10-17T07:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/39
https://digitalcommons.unl.edu/context/physicsbinek/article/1040/viewcontent/Exchange_Bias_in_Fe0.6Zn0.4F2_Fe_Heterostructures.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Exchange
Bias
Fe0.6Zn0.4F2
Heterostructures
Exchange Bias
Fe0.6Zn0.4F2 Heterostructures
Physics
oai:digitalcommons.unl.edu:physicsbinek-1042
2007-12-07T17:58:50Z
publication:physicsfacpub
publication:physicsresearch
publication:physics
publication:physicsbinek
Transverse Magnetism of the diluted antiferromagnet Fe1-xMgxBr2 (x=0.15)
Binek, Christian
Neutron diffraction and magnetization measurements of the diluted crystal Fe1−xMgxBr2 (xnot, vert, similar0.15) were performed. Successive phase transitions at zero applied field at TN1not, vert, similar12 K and TN2not, vert, similar10 K were found. A previous transverse term ferromagnetic moment was detected just below TN2.
2001-11-02T08:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/41
https://digitalcommons.unl.edu/context/physicsbinek/article/1042/viewcontent/Transverse_magnetism_of_the_diluted_antiferromagnet_Fe1_xMgxBr2_x_0.15.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Transverse
Magnetism
diluted
antiferromagnet
Fe1-xMgxBr2
Physics
oai:digitalcommons.unl.edu:physicsbinek-1047
2007-12-07T18:35:29Z
publication:physicsfacpub
publication:physicsresearch
publication:physics
publication:physicsbinek
Polydispersivity of non-critical field-induced fluctuations in FeBr2
Binek, Christian
The field and temperature dependence of the complex low-frequency susceptibility of the metamagnet FeBr2 exhibits large anomalies in the vicinity of the second-order phase boundary Hc(T). The low-frequency losses reflect polydispersive dynamics with a broad distribution of relaxation times peaking at τ ≈ 0.2 s. The dispersion, χ versus ƒ, is well described within Chamberlin's model of dynamically coupled domains. The heterogeneous glass-like response gives rise to the intuitive picture of a magnetic fluid of high viscosity.
1998-05-14T07:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/46
https://digitalcommons.unl.edu/context/physicsbinek/article/1047/viewcontent/Polydispersivity_of_non_critical_field_induced_fluctuations_in_FeBr2.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Polydispersivity
non-critical
field-induced
fluctuations
FeBr2
Physics
oai:digitalcommons.unl.edu:physicsbinek-1048
2007-12-07T18:39:25Z
publication:physicsfacpub
publication:physicsresearch
publication:physics
publication:physicsbinek
Transient spin structures at the antifero-to-paramagnetic phase boundary of FeBr2
Binek, Christian
Excess magnetization and anomalous susceptibility loss is observed on antiferromagnetic FeBr2 in an axial field H below and above its H-T-phase boundary between the multicritical temperature (Tm = 4.6 K) and the Néel temperature (TN = 14.1 K). These and other unusual properties of FeBr2 are attributed to frustration-induced intraplanar non-critical spin fluctuations, which can be simulated within the framework of a triaxial version of the 2D-ANNNI model.
2000-08-14T07:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/47
https://digitalcommons.unl.edu/context/physicsbinek/article/1048/viewcontent/Transient_spin_structures_at_the_antifero_to_paramagnetic_phase_boundary_of_FeBr2.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Transient
spin
structures
antiferro-to-paramagnetic
phase boundary
FeBr2
Physics
oai:digitalcommons.unl.edu:physicsbinek-1046
2007-12-07T18:31:46Z
publication:physicsfacpub
publication:physicsresearch
publication:physics
publication:physicsbinek
Kinetics of random-field induced domains in the two-dimensional Ising antiferromagnet Rb2Co0.85Mg0.15F4
Binek, Christian
The previous kinetics of the two-dimensional diluted Ising antiferromagnet Rb2Co0.85Mg0.15F4 is studied via the temporal relaxation of the field-induced magnetization after field cooling (FC) and zero-field cooling (ZFC), respectively, to T < TN = 75.2K. After FC different non-exponential decay laws indicate a crossover from domain reorientation to wall rearrangement at decreasing T. After ZFC rapidly saturating magnetization of naturally grown domain walls precedes the slow random-field-controlled disordering process.
1998-01-01T08:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/45
https://digitalcommons.unl.edu/context/physicsbinek/article/1046/viewcontent/Kinetics_of_random_field_induced_domains_in_the_two_dimensional_Ising_Antiferromagnet_Rb2Co0.85Mg0.15F4.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Kinetics
random-field
Ising
antiferromagnet
Rb2Co0.85Mg0.15F4
Physics
oai:digitalcommons.unl.edu:physicsbinek-1056
2007-12-07T19:10:08Z
publication:physicsfacpub
publication:physicsresearch
publication:physics
publication:physicsbinek
Superspin glass behaviour of interacting ferromagnetic nanoparticles in discontinuous magnetic multilayers
Binek, Christian
Discontinuous magnetic multilayers [Co80Fe20(t)/Al2O3(3nm)]10 with t = 0.9 and 1.0nm are studied by SQUID magnetometry and ac susceptibility. Owing to dipolar interaction the superparamagnetic cluster systems undergo collective glass-like freezing upon cooling. While both samples exhibit very similar glass temperatures Tg » 45 K and critical exponents zn » 10 and g » 1.4 as obtained from the temperature dependencies of the relaxation time, t, and the nonlinear susceptibility, c3, dynamical scaling reveals different critical exponents, b(0.9nm) »1.0 and b(1.0nm) » 0.6, respectively.
2000-10-01T07:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/55
https://digitalcommons.unl.edu/context/physicsbinek/article/1056/viewcontent/Superspin_glass_behavior_of_interacting_ferromagnetic_nanoparticles_in_discontinuous_magnetic_multilayers.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Superspin
glass
interacting
ferromagnetic
nanoparticles
discontinuous
magnetic
Physics
oai:digitalcommons.unl.edu:physicsbinek-1052
2007-12-07T18:55:25Z
publication:physicsfacpub
publication:physicsresearch
publication:physics
publication:physicsbinek
The effect of diamagnetic dilution on the spin-phonon interaction and scattering cross section in Fe1-xZnxF2
Binek, Christian
The temperature dependences of the first moments of phonon Raman scattering lines are studied for Fe1-xZnxF2. The diamagnetic dilution diminishes the spin-phonon coupling strength of phonons with both A1g and Eg symmetry in proportion to the decrease in the ordering temperature TN. Moreover, the Eg mode shows an asymmetrical lineshape for Zn concentrations x>0.3. It is explained by an unresolved superposition of two modes, one of which is ascribed to perturbed ZnF2 with broken translational symmetry.
1992-01-06T08:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/51
https://digitalcommons.unl.edu/context/physicsbinek/article/1052/viewcontent/The_effect_of_diamagnetic_dilution_on_the_spin_phonon_interaction_and_scattering_cross_section_in_Fe1___xZnxf2.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
diamagnetic
dilution
spin-phonon
scattering
cross section
Fe1-xZnxF2
Physics
oai:digitalcommons.unl.edu:physicsbinek-1054
2007-12-07T19:02:25Z
publication:physicsfacpub
publication:physicsresearch
publication:physics
publication:physicsbinek
Yang-Lee edge singularities from experimental high field magnetization data
Binek, Christian
The isothermal magnetization m(H) of the metamagnet FeCl2 is measured in axial magnetic fields 0≤µ0Ha≤12 T at temperatures 34≤T≤53 K above the Néel temperature, where the system is essentially a two-dimensional Ising ferromagnet. The analysis of the data indicates experimental accessibility of the critical exponent µ of the Yang-Lee edge singularities. They manifest themselves in divergences of the density functions g(θ), which quantify the distribution of the zeros of the partition function on the Lee-Yang unit circle in the complex plane. In accordance with the hypothesis of universality, a critical exponent close to the theoretical prediction for the two-dimensional Ising ferromagnet, µ = -1/6, is found.
2001-08-02T07:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/53
https://digitalcommons.unl.edu/context/physicsbinek/article/1054/viewcontent/Yang_Lee_edge_singularities_from_experimental_high_field_magnetization_data.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Yang-Lee
edge
singularities
high field
magnetization
Physics
oai:digitalcommons.unl.edu:physicsbinek-1050
2007-12-07T18:47:32Z
publication:physicsfacpub
publication:physicsresearch
publication:physics
publication:physicsbinek
Random-field critical and spin-flop behavior of the anisotropic Heisenberg antiferromagnet Fe0.9Mg0.1Br2 in axial magnetic fields
Binek, Christian
Faraday optical measurements on the dilute hexagonal antiferromagnet Fe0.85Mg0.15Br2 in an external axial field reveal a spin-flop phase line ending at a multicritical point (Tm=8.1 K, Hm=1050 kA m-1) and crossover from random-exchange to random-field Ising criticality with an exponent Phi =1.40+or-0.04 in the vicinity of TN=11.1 K. Cusp-like behaviour of the specific heat at TN is discussed in view of recent Monte Carlo results.
1994-02-07T08:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/49
https://digitalcommons.unl.edu/context/physicsbinek/article/1050/viewcontent/Random_field_critical_and_spin_flop_behavior_of_the_anisotropic_heisenberg_antiferromagnet_Fe0.9Mg0.1Br2_in_axial_magnetic_fields.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Random-field
critical
spin-flop
behavior
anisotropic
Heisenberg
antiferromagnet
Fe0.9Mg0.1Br2
axial
magnetic
fields
Physics
oai:digitalcommons.unl.edu:physicsbinek-1051
2007-12-07T18:50:49Z
publication:physicsfacpub
publication:physicsresearch
publication:physics
publication:physicsbinek
Light diffraction by field-induced non-periodic magnetic domain structures in FeCl2
Binek, Christian
The magnetic-field-induced mixed phase of the meta magnet FeCl2 gives rise to reduced transmittivity of circularly polarized light. Within the framework of the diffraction theory of thin random magnetic phase gratings and the assumption of field-dependent refractive indices of the antiferromagnetic domains the field dependence of the transmission is perfectly modeled.
1993-05-24T07:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/50
https://digitalcommons.unl.edu/context/physicsbinek/article/1051/viewcontent/Light_diffraction_by_field_induced_non_periodic_magnetic_domain_structures_in_FeCl2.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Light
diffraction
field-induced
non-periodic
magnetic
domain
structures
FeCl2
Physics
oai:digitalcommons.unl.edu:physicsbinek-1049
2007-12-07T18:42:42Z
publication:physicsfacpub
publication:physicsresearch
publication:physics
publication:physicsbinek
Crossover from transient spin structures ot the field-induced Griffiths phase of FeBr2
Binek, Christian
In the presence of an applied axial magnetic field Ha the uniaxial antiferromagnets FeCl2 and FeBr2 show fluctuating domain-like antiferromagnetic correlations above the phase boundary Tc(Ha). They are detected by SQUID measurements of the low frequency out-of-phase susceptibility gc″ and indicate a field-induced Griffiths phase at temperatures Tc(Ha) < T < TN. In contrast to FeCl2, important additional frustration-induced intraplanar non-critical contributions to χ″ vs. T are found in FeBr2. For external fields above the Tc(Ha) line, Ha > 2.6 MA/m, they are shown to superimpose linearly on the Griffiths contributions. These dominate at Ha = 2.67 MA/m and are unequivocally modeled within the Landau theory of fluctuations near phase transitions by introducing a Lorentzian Tc distribution.
2000-08-14T07:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/48
https://digitalcommons.unl.edu/context/physicsbinek/article/1049/viewcontent/Crossover_from_transient_spin_structures_to_the_field_induced_Griffiths_Phase_of_FeBr2.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
crossover
transient
spin
structures
field-induced
Griffiths
FeBr2
Physics
oai:digitalcommons.unl.edu:physicsbinek-1055
2007-12-07T19:06:52Z
publication:physicsfacpub
publication:physicsresearch
publication:physics
publication:physicsbinek
Domain state susceptibility in FeCl2/CoPt-heterostructures
Binek, Christian
Magnetic heterostructures with perpendicular anisotropy consisting of antiferromagnetic (111)-oriented FeCl2 single crystals and thin ferromagnetic CoPt-multilayers are investigated by ac-susceptometry after cooling in various axial magnetic fields to below the Néel temperature. The freezing process drives the system into a metastable antiferromagnetic domain state which gives rise to a huge excess contribution to the complex parallel susceptibility on heating in zero magnetic field. Its glow curve-like temperature dependence is modeled within the framework of a simple analytical approach. It involves the susceptibility of thermally activated clusters originating from antiferromagnetic stacking faults as well as the contribution of pairs of antiparallel Ising spins which build up walls within the ferromagnetically ordered (111) planes.
2001-09-30T07:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/54
https://digitalcommons.unl.edu/context/physicsbinek/article/1055/viewcontent/Domain_state_susceptibility_in_FeCl2_Copt_heterostructures.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Domain
state
susceptibility
FeCl2/CoPt-heterostructures
heterostructures
Physics
oai:digitalcommons.unl.edu:physicsbinek-1057
2008-02-07T16:11:39Z
publication:physicsfacpub
publication:mrsecfacpubs
publication:physicsresearch
publication:physics
publication:physicsbinek
publication:materialsresearchscieeng
Scaling Behavior of the Exchange-Bias Training Effect
Binek, Christian
Polisetty, Srinivas
Sahoo, Sarbeswar
The dependence of the exchange-bias training effect on temperature and ferromagnetic film thickness is studied in detail and scaling behavior of the data is presented. Thickness-dependent exchange bias and its training are measured using the magneto-optical Kerr effect. A focused laser beam is scanned across a Co wedge probing local hysteresis loops of the Co film which is pinned by an antiferromagnetic CoO layer of uniform thickness. A phenomenological theory is best fitted to the exchange-bias training data resembling the evolution of the exchange-bias field on subsequently cycled hysteresis loops. Best fits are done for various temperatures and Co thicknesses. Data collapse on respective master curves is achieved for the thickness and temperature-dependent fitting parameters as well as the exchange bias and coercive fields of the initial hysteresis loops. The scaling behavior is strong evidence for the validity and the universality of the underlying theoretical approach based on triggered relaxation of the pinning layer towards quasiequilibrium.
2007-08-27T07:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/56
https://digitalcommons.unl.edu/context/physicsbinek/article/1057/viewcontent/Scaling_Behavior_of_the_exchange_bias_training_effect.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Scaling
behavior
exchange-bias
training
effect
Physics
oai:digitalcommons.unl.edu:physicsbinek-1059
2008-06-02T19:41:24Z
publication:physicsfacpub
publication:mrsecfacpubs
publication:physicsresearch
publication:physics
publication:physicsbinek
publication:materialsresearchscieeng
Optimization of Magneto-Optical Kerr Setup: Analyzing experimental assemblies using Jones matrix formalism
Binek, Christian
We present a comparative study on an experimental and theoretical optimization of magneto-optical Kerr setups based on photoelastic modulation and phase sensitive detector methodology. The first and second harmonics, Iomega,2omega, of the reflected light intensity are measured for a CoO/Co magnetic reference film. The magnetic field dependence of the optical off-diagonal Fresnel reflection coefficients rps and rsp follows the sample magnetization. Different Kerr setups provide various dependencies of Iomega,2omega on the reflection coefficients and, hence, on the Kerr ellipticity epsilonK and rotation thetaK. Jones matrix formalism has been used to analyze the impact of a systematic variation of relative analyzer and polarizer orientations with respect to each other and with respect to the retardation axis of the modulator involved in longitudinal Kerr setups for incoming s-polarized light. We find one particular setup which maximizes Iomega as well as I2omega and maximizes the signal-to-noise ratio. Inefficient setups are characterized by Iomega,2omega intensities involving large nonmagnetic contributions of rp and rs.
2008-05-28T07:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/60
https://digitalcommons.unl.edu/context/physicsbinek/article/1059/viewcontent/Optimization_of_magneto_optical_Kerr_setup.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Optimization
magneto-optical
kerr
analyzing
experimental
assemblies
jones
matrix
formalism
Physics
oai:digitalcommons.unl.edu:physicsskomski-1052
2017-04-11T18:39:24Z
publication:physicsskomski
publication:physicsfacpub
publication:mrsecfacpubs
publication:physicsresearch
publication:physics
publication:physicsbinek
publication:materialsresearchscieeng
publication:physicssellmyer
Temperature- and field-induced entropy changes in nanomagnets
Skomski, Ralph
Binek, Christian
Mukherjee, Tathagata
Sahoo, Sarbeswar
Sellmyer, David J.
Room-temperature magnetic-entropy changes in nanostructures for magnetic refrigeration are investigated by model calculations. Using a mean-field approach, the magnetic entropy is calculated as a function of temperature, magnetic field, particle size, anisotropy, and interaction strength. Both isotropic (Heisenberg) and uniaxial (Ising and XY) anisotropies are considered. The nanoparticle entropy strongly depends on the character of the anisotropy, in contrast to atomic ferromagnetism, where the anisotropy energy is much smaller than the interaction energy. Most promising are isotropic particles and particles with weak easy axis anisotropy, as well as easy-plane particle with the field in the plane. The optimum nanoparticle size is not much larger than 1 nm, because the relative magnetization direction in a nanoparticle is usually frozen and do not contribute to the entropy change.
2008-02-28T08:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsskomski/53
https://digitalcommons.unl.edu/context/physicsskomski/article/1052/viewcontent/Skomski_JAP_2008_Temperature_and_field_induced.pdf
Ralph Skomski Publications
DigitalCommons@University of Nebraska - Lincoln
Physics
oai:digitalcommons.unl.edu:physicsbinek-1060
2008-11-25T19:22:48Z
publication:physicsfacpub
publication:physicsresearch
publication:physics
publication:physicsbinek
Temperature dependence of the training effect in exchange coupled ferromagnetic bilayers
Binek, Christian
Polisetty, Srinivas
Sahoo, Sarbeswar
The temperature dependence of the training effect is studied in an exchange coupled thin-film bilayer composed of a hard ferromagnetic pinning (CoPtCrB) layer in proximity of a soft ferromagnetic pinned (CoCr) layer. Interlayer exchange shifts the hysteresis loops of the soft layer along the magnetic-field axis. This shift is quantified by the bias field in far reaching analogy to the exchange bias field of conventional antiferromagnetic/ferromagnetic heterostructures. A ferromagnetic domain state induced in the hard layer experiences aging very similar to the training behavior of the antiferromagnetic domain state in conventional exchange bias systems. Training originates from changes in the spin structure of the pinning layer with consecutive magnetization reversals of the pinned layer. Here we perform a detailed investigation of the temperature dependence of the bias field and its training effect. Consecutively cycled hysteresis loops of the soft layer are measured at various temperatures. We also derive a theoretical description of the temperature dependence of the training effect which is in agreement with the experimental data.
2008-11-20T08:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/62
https://digitalcommons.unl.edu/context/physicsbinek/article/1060/viewcontent/Temperature_dependence_of_the_training_effect_in_exchange_coupled_ferromagnetic_bilayers.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Temperature
dependence
training
effect
exchange
coupled
ferromagnetic
bilayers
Physics
oai:digitalcommons.unl.edu:physicsbinek-1061
2009-04-07T16:08:11Z
publication:physicsfacpub
publication:mrsecfacpubs
publication:physicsresearch
publication:physics
publication:physicsbinek
publication:materialsresearchscieeng
Temperature Dependence of the Training Effect in Exchange Coupled Ferromagnetic Bilayers
Polisetty, Srinivas
Sahoo, Sarbeswar
Berger, Andreas
Binek, Christian
The temperature dependence of the training effect is studied in an exchange coupled thin-film bilayer composed of a hard ferromagnetic pinning (CoPtCrB) layer in proximity of a soft ferromagnetic pinned (CoCr) layer. Interlayer exchange shifts the hysteresis loops of the soft layer along the magnetic-field axis. This shift is quantified by the bias field in far reaching analogy to the exchange bias field of conventional antiferromagnetic/ferromagnetic heterostructures. A ferromagnetic domain state induced in the hard layer experiences aging very similar to the training behavior of the antiferromagnetic domain state in conventional exchange bias systems. Training originates from changes in the spin structure of the pinning layer with consecutive magnetization reversals of the pinned layer. Here we perform a detailed investigation of the temperature dependence of the bias field and its training effect. Consecutively cycled hysteresis loops of the soft layer are measured at various temperatures. We also derive a theoretical description of the temperature dependence of the training effect which is in agreement with the experimental data.
2008-01-01T08:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/61
https://digitalcommons.unl.edu/context/physicsbinek/article/1061/viewcontent/Binek_PRB_2008_Temperature_dependence.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Physics
oai:digitalcommons.unl.edu:physicsbinek-1063
2017-04-11T18:45:15Z
publication:physicsfacpub
publication:physicsresearch
publication:physics
publication:physicsbinek
publication:physicssellmyer
Magnetocaloric properties of Co/Cr superlattices
Mukherjee, Tathagata
Sahoo, Sarbeswar
Sellmyer, David J
Binek, Christian
Nanostructured materials for refrigeration applications are experimentally realized by molecular beam epitaxial growth of Co/Cr superlattices using mean-field theoretical concepts as guiding principles. Magnetocaloric properties are deduced from measurements of the temperature and field dependence of the magnetization of our samples. More generally, the potential of artificial antiferromagnets for near room-temperature refrigeration is explored. The effects of intraplane and interplane exchange interactions on the magnetic phase diagram in Ising-type model systems are revisited in mean-field considerations with special emphasis on tailoring magnetocaloric properties. The experimental results are discussed in light of our theoretical findings, and extrapolations for future improved nanostructures are provided.
2009-04-07T07:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/66
https://digitalcommons.unl.edu/context/physicsbinek/article/1063/viewcontent/Magnetocaloric_properties_of_cocr_superlattices.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Magnetocaloric
properties
Co
Cr
Co/Cr
superlattice
superlattices
Physics
oai:digitalcommons.unl.edu:physicsbinek-1064
2009-05-11T17:11:26Z
publication:physicsfacpub
publication:physicsresearch
publication:physics
publication:physicsbinek
Electrically Controlled Magnetism
Binek, Christian
He, Xi
Wang, Yi
Sahoo, Sarbeswar
Manipulation of magnetically ordered states by electrical means is a promising approach towards novel spintronics devices. We report on the electric control of surface magnetism in Cr2O3 thin films and uniaxial anisotropy in ferroelectric/ferromagnetic heterostructures, respectively. Artificial magnetoelectricity is realized in a BaTiO3/Fe heterostructure. Here, thermally induced coercivity changes of the Fe hysteresis loop are used to derive the stress imposed by the ferroelectric BaTiO3 substrate on the adjacent Fe film. Electrically induced coercivity changes give rise to a giant magnetoelectric susceptibility in the vicinity of the magnetic coercive field.
2008-09-04T07:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/65
https://digitalcommons.unl.edu/context/physicsbinek/article/1064/viewcontent/Electrically_Controlled_Magnetism.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
electrically
controlled
magnetism
electric
magnet
control
Physics
oai:digitalcommons.unl.edu:physicsbinek-1065
2009-05-11T17:15:51Z
publication:physicsfacpub
publication:physicsresearch
publication:physics
publication:physicsbinek
Quenching of the Exchange Bias Training in Fe/Cr2O3/Fe Trilayer
Sahoo, Sarbeswar
Binek, Christian
Exchange bias (EB) and its associated training effects are studied in an epitaxial Fe(10 nm)/Cr2O3(2.7 nm)/Fe(10 nm) trilayer heterostructure grown by molecular beam epitaxy. The EB decreases linearly with increasing temperature from T = 5 K to T = 50 K. It changes sign and becomes positive within 50 K < T < 200 K, finally changing back to regular EB for T<200K up to the highest measured temperature of T = 395 K. Remarkably, the latter is far above the bulk Néel temperature TN = 307 K. EB training effects occur only at 5 K < T < 50 K. We show that this training can be quenched by subjecting the system to DC magnetic field, µ0HDC <= 7 T. The applied field most likely induces a temperature dependent spin-flop transition. Upon its removal the antiferromagnetic Cr2O3 pinning layer evolves uniformly into its quasi-equilibrium spin configuration thus leading to quasi-equilibrium EB.
2008-10-23T07:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/64
https://digitalcommons.unl.edu/context/physicsbinek/article/1065/viewcontent/Quenching_of_the_exchange_bias.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Quenching
Exchange
Bias
Training
Fe
Cr
Cr2
Cr2O3
Fe
Trilayer
Physics
oai:digitalcommons.unl.edu:physicsbinek-1066
2009-06-19T16:17:50Z
publication:physicsfacpub
publication:physicsresearch
publication:physics
publication:physicsbinek
Self-Assembly of Magnetic Ni Nanoparticles into 1D Arrays with Antiferromagnetic Order
Bliznyuk, Valery
Singamaneni, Srikanth
Sahoo, Sarbeswar
Polisetty, Srinivas
He, Xi
Binek, Christian
In this paper, we report on the magnetic properties of isolated nanoparticles and interacting nanochains formed by the self-assembly of Ni nanoparticles. The magnetic properties were studied using superconducting quantum interference device (SQUID) magnetometry and magnetic force microscopy (MFM). We demonstrate that single-domain Ni nanoparticles spontaneously form one-dimensional (1D) chains under the influence of an external magnetic field. Furthermore, such magnetic field-driven self-assembly in conjunction with surface templating produces regular arrays of 1D nanochains with antiferromagnetic intra-chain order. The antiferromagnetic order, which is in striking contrast to what is found for non-interacting nanoparticle assemblies within the chains, can be evidenced from MFM and SQUID measurements.
2009-01-01T08:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/63
https://digitalcommons.unl.edu/context/physicsbinek/article/1066/viewcontent/Binek_NANOTECH_2009_Self_assembly__DC_VERSION.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Physics
oai:digitalcommons.unl.edu:physicsskomski-1060
2017-04-11T18:41:00Z
publication:physicsskomski
publication:mrsecfacpubs
publication:physicsresearch
publication:physics
publication:physicsbinek
publication:materialsresearchscieeng
publication:physicsenders
publication:physicssellmyer
Entropy localization in magnetic compounds and thin-film nanostructures
Skomski, Ralph
Binek, Christian
Michalski, Steven A.
Mukherjee, Tathagata
Enders, Axel
Sellmyer, David J.
The effect of nanostructuring on the magnetic entropy of materials for room-temperature magnetic cooling is investigated by model calculations. The materials are structurally inhomogeneous with a large number of nonequivalent crystallographic sites. In the mean-field Heisenberg model, the entropy density is a unique function of the local magnetization so that the coupled set of nonlinear mean-field equations yields not only the magnetization but also the entropy density. Since most of the entropy is localized near grain boundaries, nanomagnetic cooling requires small feature sizes. Magnetic anisotropy is a substantial complication, even on a mean-field level, but the corresponding corrections are often very small.
2010-01-01T08:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsskomski/68
https://digitalcommons.unl.edu/context/physicsskomski/article/1060/viewcontent/Skomski_JAP_2010_Entropy_localization.pdf
Ralph Skomski Publications
DigitalCommons@University of Nebraska - Lincoln
Physics
oai:digitalcommons.unl.edu:physicsbinek-1067
2017-02-24T14:36:55Z
publication:mrsecfacpubs
publication:physicsresearch
publication:physicsdowben
publication:physics
publication:physicsbinek
publication:materialsresearchscieeng
Robust isothermal electric control of exchange bias at room temperature
He, Xi
Wang, Yi
Binek, Christian
Dowben, Peter A.
Voltage-controlled spin electronics is crucial for continued progress in information technology. It aims at reduced power consumption, increased integration density and enhanced functionality where non-volatile memory is combined with highspeed logical processing. Promising spintronic device concepts use the electric control of interface and surface magnetization. From the combination of magnetometry, spin-polarized photoemission spectroscopy, symmetry arguments and first-principles calculations, we show that the (0001) surface of magnetoelectric Cr2O3 has a roughness-insensitive, electrically switchable magnetization. Using a ferromagnetic Pd/Co multilayer deposited on the (0001) surface of a Cr2O3 single crystal, we achieve reversible, room-temperature isothermal switching of the exchange-bias field between positive and negative values by reversing the electric field while maintaining a permanent magnetic field. This effect reflects the switching of the bulk antiferromagnetic domain state and the interface magnetization coupled to it. The switchable exchange bias sets in exactly at the bulk Néel temperature.
2010-06-20T07:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/68
https://digitalcommons.unl.edu/context/physicsbinek/article/1067/viewcontent/nmat2785.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Robust
isothermal
exchange
bias
electric
control
room
temperature
Condensed Matter Physics
Physics
oai:digitalcommons.unl.edu:physicsbinek-1068
2011-04-01T19:03:26Z
publication:mrsecfacpubs
publication:physicsresearch
publication:physics
publication:physicsbinek
publication:materialsresearchscieeng
Piezoelectric tuning of exchange bias in a BaTiO<sub>3</sub>/Co/CoO heterostructure
Polisetty, Srinivas
Echtenkamp, W.
Jones, Keith
He, X.
Sahoo, Sarbeswar
Binek, Christian
Piezoelectrically controlled strain is used for electric tuning of exchange-bias fields. A generic exchange-bias Co/CoO bilayer is deposited on the surface of a ferroelectric and thus piezoelectric BaTiO3 substrate which allows to apply electrically and thermally tunable stress in the adjacent ferromagnetic Co thin film. The stress-induced strain alters foremost the magnetic anisotropy of the Co film and by that the magnetization orientation at the Co/CoO interface modifying the exchange-bias field. This results in a pronounced electrically induced weakening of the exchange bias but also includes the possibility of tuning the exchange-bias field through a subtle sign change from regular negative to positive values. The electrically controlled crossover from negative to positive exchange bias is consistently observed at various temperatures in the rhombohedral phase of BaTiO3. This complex electric field dependence of the exchange-bias field is the result of the long-range nature of strain and interpreted through competition between ferromagnetic and antiferromagnetic exchange at the Co/CoO interface. Our data suggest competition between regular negative and positive exchange bias. Weakening of negative exchange bias originates from noncollinear alignment of the Co and CoO interface magnetizations. Positive exchange bias is activated when stress induces antiferromagnetic exchange through atomic displacements changing the exchange paths at the Co/CoO interface.
2010-01-01T08:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/69
https://digitalcommons.unl.edu/context/physicsbinek/article/1068/viewcontent/PhysRevB.82.134419.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Physics
oai:digitalcommons.unl.edu:physicsbinek-1069
2011-04-01T19:07:34Z
publication:mrsecfacpubs
publication:physicsresearch
publication:physics
publication:physicsbinek
publication:materialsresearchscieeng
Probing equilibrium by nonequilibrium dynamics: Aging in Co/Cr superlattices
Mukherjee, Tathagata
Pleimling, M.
Binek, Christian
Magnetization relaxation is investigated in a structurally ordered magnetic Co/Cr superlattice. Tailored nanoscale periodicity creates mesoscopic spatial magnetic correlations with slow relaxation dynamics when quenching the system into a nonequilibrium state. Magnetization transients are measured after exposing the heterostructure to a magnetic set field for various waiting times. Scaling analysis reveals an asymptotic powerlaw behavior in accordance with a full aging scenario. The temperature dependence of the relaxation exponent shows pronounced anomalies at the equilibrium phase transitions of the antiferromagnetic superstructure and the ferromagnetic to paramagnetic transition of the Co layers. The latter leaves only weak fingerprints in the equilibrium magnetic behavior but gives rise to a prominent change in nonequilibrium properties. Our findings suggest scaling analysis of nonequilibrium data as a probe for weak equilibrium phase transitions.
2010-01-01T08:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/70
https://digitalcommons.unl.edu/context/physicsbinek/article/1069/viewcontent/PhysRevB.82.134425.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Physics
oai:digitalcommons.unl.edu:physicsbinek-1070
2011-05-24T19:38:10Z
publication:physicsskomski
publication:mrsecfacpubs
publication:physicsresearch
publication:physics
publication:physicsbinek
publication:materialsresearchscieeng
publication:physicssellmyer
Magnetic entropy changes in nanogranular Fe:Ni<sub>61</sub>Cu<sub>39</sub>
Michalski, Steven A.
Skomski, Ralph A.
Mukherjee, Tathagata
Li, Xingzhong
Binek, Christian
Sellmyer, David J.
Artificial environment-friendly Gd-free magnetic nanostructures for magnetic cooling are investigated by temperature-dependent magnetic measurements. We consider two-phase nanocomposites where nanoclusters (Fe) are embedded in a Ni61Cu39 matrix. Several composite films are produced by cluster deposition. The average Fe cluster size depends on the deposition conditions and can be tuned by varying the deposition conditions. The quasiequilibrium Curie temperature of the Fe particles is high, but slightly lower than that of bulk Fe due to finite-size effects. Our experiments have focused on ensembles of 7.7 nm Fe clusters in a matrix with a composition close to Ni61Cu39, which has a TC of 180 K. The materials are magnetically soft, with coercivities of order 16 Oe even at relatively low temperature of 100 K. The entropy changes are modest, –ΔS = 0.05 J/kg K in a field change of 1 T and 0.30 J/kg K in a field change of 7 T at a temperature of 180 K, which should improve if the cluster size is reduced.
2011-04-01T07:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/71
https://digitalcommons.unl.edu/context/physicsbinek/article/1070/viewcontent/JApplPhys_109_07A936.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Physics
oai:digitalcommons.unl.edu:physicsbinek-1071
2017-02-24T15:54:02Z
publication:mrsecfacpubs
publication:physicsresearch
publication:physicsdowben
publication:physics
publication:physicsbinek
publication:materialsresearchscieeng
When measured spin polarization is not spin polarization
Dowben, Peter A.
Wu, Ning
Binek, Christian
Spin polarization is an unusually ambiguous scientific idiom and, as such, is rarely well defined. A given experimental methodology may allow one to quantify a spin polarization but only in its particular context. As one might expect, these ambiguities sometimes give rise to inappropriate interpretations when comparing the spin polarizations determined through different methods. The spin polarization of CrO2 and Cr2O3 illustrate some of the complications which hinders comparisons of spin polarization values.
2011-04-01T07:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/72
https://digitalcommons.unl.edu/context/physicsbinek/article/1071/viewcontent/Binek_JPCM_2011_When_measured_spin.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Physics
oai:digitalcommons.unl.edu:physicsbinek-1072
2017-03-01T21:42:12Z
publication:mrsecfacpubs
publication:physicsresearch
publication:physicsdowben
publication:physicsbelashchenko
publication:physics
publication:physicsbinek
publication:materialsresearchscieeng
Imaging and Control of Surface Magnetization Domains in a Magnetoelectric Antiferromagnet
Wu, Ning
He, Xi
Wysocki, Aleksander L.
Lanke, Uday
Komesu, Takashi
Belashchenko, Kirill D.
Binek, Christian
Dowben, Peter A.
We report the direct observation of surface magnetization domains of the magnetoelectric Cr2O3 using photoemission electron microscopy with magnetic circular dichroism contrast and magnetic force microscopy. The domain pattern is strongly affected by the applied electric field conditions. Zero-field cooling results in an equal representation of the two domain types, while electric-field cooling selects one dominant domain type. These observations confirm the existence of surface magnetization, required by symmetry in magnetoelectric antiferromagnets.
2011-02-01T08:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/73
https://digitalcommons.unl.edu/context/physicsbinek/article/1072/viewcontent/PhysRevLett.106.087202.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Physics
oai:digitalcommons.unl.edu:physicssellmyer-1226
2017-04-11T18:33:20Z
publication:physicsskomski
publication:physicsresearch
publication:physics
publication:physicsbinek
publication:physicssellmyer
Spin and elastic contributions to isothermal entropy change
Mukherjee, Tathagata
Skomski, Ralph
Michalski, Steven A.
Sellmyer, David J.
Binek, Christian
Statistical considerations of ensembles of localized magnetic moments reveal an upper bound of the isothermal entropy change when only the magnetic degrees of freedom are considered. In this case, the maximum molar isothermal entropy change is determined by the spin multiplicity and is equal to Rln(2J+1), where J is the angular momentum of an individual atom. However, in materials with giant magnetocaloric effect, the isothermal field-induced entropy change goes beyond the spin-multiplicity limit due to field-activated elastic degrees of freedom. Recently, we investigated a model of pairs of exchange-coupled Ising spins with variable real-space positions. We showed, within a classical approximation for the elastic degree of freedom, that a vibrational entropy contribution can be activated via applied magnetic fields. Here we quantify the impact of quantum corrections in the low-temperature limit. We compare calculations that include elastic interaction with the rigid exchange model in the high-temperature limit. We find that quantum effects provide quantitative corrections in the low-temperature limit. In addition we show that the elastic contributions to the isothermal entropy change can be additive but, remarkably, it can also give rise to reduced isothermal entropy change in certain temperature regions.
2012-01-01T08:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicssellmyer/227
https://digitalcommons.unl.edu/context/physicssellmyer/article/1226/viewcontent/JApplPhys_111_07A931_Spin_and_elastic.pdf
David Sellmyer Publications
DigitalCommons@University of Nebraska - Lincoln
Physics
oai:digitalcommons.unl.edu:physicssellmyer-1225
2017-04-11T18:36:19Z
publication:physicsskomski
publication:physicsresearch
publication:physics
publication:physicsbinek
publication:physicssellmyer
Isothermal entropy changes in nanocomposite Co:Ni<sub>67</sub>Cu<sub>33</sub>
Michalski, Steven A.
Skomski, Ralph
Li, Xingzhong
Le Roy, Damien
Mukherjee, Tathagata
Binek, Christian
Sellmyer, David J.
The temperature-dependent magnetic properties of artificial rare-earth, free-magnetic nanostructures are investigated for magnetic cooling. We consider two-phase nanocomposites, where 2 nm nanoclusters of cobalt are embedded in a Ni67Cu33 matrix. Several composite films were produced by cluster deposition. The average Co nanocluster size can be tuned by varying the deposition conditions. Isothermalmagnetization curves weremeasured at various temperatures 150K
2012-01-01T08:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicssellmyer/226
https://digitalcommons.unl.edu/context/physicssellmyer/article/1225/viewcontent/JApplPhys_111_07A930_Isothermal.pdf
David Sellmyer Publications
DigitalCommons@University of Nebraska - Lincoln
Physics
oai:digitalcommons.unl.edu:physicsbinek-1075
2017-04-11T18:34:45Z
publication:mrsecfacpubs
publication:physicsresearch
publication:physics
publication:physicsbinek
publication:materialsresearchscieeng
Magnetometry and transport data complement polarized neutron reflectometry in magnetic depth profiling
Wang, Yi
He, Xi
Mukherjee, Tathagata
Fitzsimmons, Mary Lee
Sahoo, Sarbeswar
Binek, Christian
Exchange coupled magnetic hard layer/soft layer thin films show a variety of complex magnetization reversal mechanisms depending on the hierarchy of interaction strengths within and between the films. Magnetization reversal can include uniform rotation, soft layer biasing, as well as exchange spring behavior. We investigate the magnetization reversal of a CoPt/Permalloy/Ta/Permalloy heterostructure. Here, Stoner-Wohlfarth-type uniform magnetization rotation of the virtually free Permalloy layer and exchange spring behavior of the strongly pinned Permalloy layer are found in the same sample. We investigate the complex magnetization reversal by polarized neutron reflectometry, magnetometry, and magneto-transport. The synergy of combining these experimental methods together with theoretical modeling is key to obtain the complete quantitative depth resolved information of the magnetization reversal processes for a multilayer of mesoscopic thickness.
2011-01-01T08:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/76
https://digitalcommons.unl.edu/context/physicsbinek/article/1075/viewcontent/JApplPhys_110_103914_Magnetometry_and_transport_data.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Physics
oai:digitalcommons.unl.edu:physicsgruverman-1057
2017-02-25T21:57:23Z
publication:physicsgruverman
publication:mrsecfacpubs
publication:physicsresearch
publication:physicstsymbal
publication:physicsdowben
publication:physics
publication:physicsbinek
publication:materialsresearchscieeng
Electric modulation of magnetization at the BaTiO3/La0.67Sr0.33MnO3
interfaces
Lu, H.
George, Thomas A.
Wang, Yong
Ketsman, Ihor
Burton, John D.
Bark, C.-W.
Ryu, Sangjin
Jik Kim, Dong
Wang, J.
Binek, Christian
Dowben, Peter A.
Sokolov, Andrei
Eom, C. B.
Tsymbal, Evgeny Y.
Gruverman, Alexei
We report large (>10%) magnetization modulation by ferroelectric polarization reversal in the ferroelectric-ferromagnetic BaTiO3/La0.67Sr0.33MnO3 (BTO/LSMO) heterostructures. We find that the electrically induced change in magnetization is limited to the BTO/LSMO interface but extends about 3 nm deep into the LSMO layer—far beyond the expected screening length of metallic LSMO. It is suggested that this effect is due to a metal-insulator transition occurring at the BTO/LSMO interface as a result of electrostatic doping.
2012-01-01T08:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsgruverman/58
https://digitalcommons.unl.edu/context/physicsgruverman/article/1057/viewcontent/ApplPhysLett_100_232904.pdf
Alexei Gruverman Publications
DigitalCommons@University of Nebraska - Lincoln
Physics
oai:digitalcommons.unl.edu:physicsskomski-1085
2017-04-11T18:37:30Z
publication:physicsskomski
publication:physicsresearch
publication:physics
publication:physicsbinek
publication:physicssellmyer
Overcoming the spin-multiplicity limit of entropy by means of lattice degrees of freedom:
A minimal model
Mukherjee, Tathagata
Michalski, Steven A.
Skomski, Ralph
Sellmyer, David J
Binek, Christian
The discovery of the giant magnetocaloric effect with isothermal field-induced entropy change beyond the spin-multiplicity limit gave rise to some indistinctness in the literature regarding the applicability of fundamental thermodynamics in data analysis. Those misleading interpretations concerning, for instance, the rigorousness of phenomenological thermodynamics are clarified here. Specifically, it is shown that the Maxwell relation incorporates contributions from the spin degrees of freedom and potential lattice degrees of freedom into the isothermal entropy change. A minimalist model involving pairs of exchange-coupled, mobile Ising spins is investigated. It is explicitly shown that lattice degrees of freedom can be activated via applied magnetic fields and the integrated Maxwell relation contains this lattice contribution. A simple and intuitive analytic expression for the isothermal entropy change in the presence of field-activated lattice degrees of freedom is provided.
2011-01-01T08:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsskomski/86
https://digitalcommons.unl.edu/context/physicsskomski/article/1085/viewcontent/Skomski_PRB_2011_Overcoming_the_spin_multiplicity_limit.pdf
Ralph Skomski Publications
DigitalCommons@University of Nebraska - Lincoln
oai:digitalcommons.unl.edu:physicsdowben-1256
2017-04-25T14:23:22Z
publication:mrsecfacpubs
publication:physicsresearch
publication:physicsdowben
publication:physics
publication:physicsbinek
publication:materialsresearchscieeng
Increasing the Neel temperature of magnetoelectric chromia for voltage-controlled spintronics
Street, M
Echtenkamp, W
Komesu, Takashi
Cao, Shi
Dowben, Peter A.
Binek, Christian
Boron doped chromia (Cr2O3) thin films with substitutional doping levels between zero and 3% are grown using pulsed laser deposition in borane background gases. Magnetometry reveals a tunable increase in the Neel temperature of the (0001) textured Cr2BxO3-x thin films at a rate of about 10% with 1% oxygen site substitution preserving a net boundary magnetization. Spin resolved inverse photoemission measured after magnetoelectric annealing in subsequently reversed electric fields evidences voltage-controlled reversal of boundary magnetization and thus magnetoelectricity of Cr2BxO3-x. Conservation of magnetoelectricity far above room temperature makes ultra-low power voltage-controlled spintronic devices feasible.
2014-01-01T08:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsdowben/257
https://digitalcommons.unl.edu/context/physicsdowben/article/1256/viewcontent/Dowben_APL_2014_Increasing_the_Neel_temperature.pdf
Peter Dowben Publications
DigitalCommons@University of Nebraska - Lincoln
Physical Sciences and Mathematics
Physics
oai:digitalcommons.unl.edu:physicsdowben-1262
2017-04-25T14:26:57Z
publication:mrsecfacpubs
publication:physicsresearch
publication:physicsdowben
publication:physics
publication:physicsbinek
publication:materialsresearchscieeng
Spin polarization asymmetry at the surface of chromia
Cao, Shi
Zhang, Xin
Wu, Ning
N'Diaye, A T
Chen, G
Schmid, A K
Chen, Xumin
Echtenkamp, W
Enders, Axel
Binek, Christian
Dowben, Peter A.
We demonstrate boundary spin polarization at the surface of a Cr2O3 single crystal using spin-polarized low-energy electron microscopy (SPLEEM), complementing prior spin polarized photoemission, spin polarized inverse photoemission, and x-ray magnetic circular dichroism photoemission electron microscopy measurements. This work shows that placing a Cr2O3 single crystal into a single domain state will result in net Cr2O3 spin polarization at the boundary, even in the presence of a gold overlayer. There are indications that the SPLEEM contrast for the two polarization states may be different, consistent with scanning tunneling microscopy spectroscopy results obtained from ultrathin films of Cr2O3.
2014-01-01T08:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsdowben/263
https://digitalcommons.unl.edu/context/physicsdowben/article/1262/viewcontent/Dowben_NJP_2014_Spin_polarization_asymmetry.pdf
Peter Dowben Publications
DigitalCommons@University of Nebraska - Lincoln
magnetoelectrics
surface spin polarization
voltage control of spin
surface and interface dipoles
Physical Sciences and Mathematics
Physics
oai:digitalcommons.unl.edu:physicsbinek-1077
2016-05-24T17:10:08Z
publication:mrsecfacpubs
publication:physicsresearch
publication:physics
publication:physicsbinek
publication:materialsresearchscieeng
Magnetic field induced switching of the antiferromagnetic order parameter in thin films of magnetoelectric chromia
Fallarino, Lorenzo
Berger, Andreas
Binek, Christian
A Landau-theoretical approach is utilized to model the magnetic field induced reversal of the antiferromagnetic order parameter in thin films of magnetoelectric antiferromagnets. A key ingredient of this peculiar switching phenomenon is the presence of a robust spin polarized state at the surface of the antiferromagnetic films. Surface or boundary magnetization is symmetry allowed in magnetoelectric antiferromagnets and experimentally established for chromia thin films. It couples rigidly to the antiferromagnetic order parameter and its Zeeman energy creates a pathway to switch the antiferromagnet via magnetic field application. In the framework of a minimalist Landau free energy expansion, the temperature dependence of the switching field and the field dependence of the transition width are derived. Least-squares fits to magnetometry data of (0001) textured chromia thin films strongly support this model of the magnetic reversal mechanism.
2015-02-15T08:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/79
https://digitalcommons.unl.edu/context/physicsbinek/article/1077/viewcontent/PhysRevB.91.054414.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
chromia
magnetoelectric
oai:digitalcommons.unl.edu:physicsbinek-1078
2016-05-24T17:16:11Z
publication:mrsecfacpubs
publication:physicsresearch
publication:physics
publication:physicsbinek
publication:materialsresearchscieeng
Boundary magnetization properties of epitaxial Cr2−xAlxO3 thin films
Fallarino, Lorenzo
Binek, Christian
Berger, Andreas
The magnetoelectric antiferromagnet α-Cr2O3 (chromia) is known to possess a roughness insensitive net equilibrium magnetization at the (0001) surface, called boundary magnetization (BM), which is coupled to the bulk antiferromagnetic order parameter. In order to verify whether this symmetry sensitive BM persists in alloys, we investigate the impact of diamagnetic dilution on chromia thin films alloyed with the isostructural α-Al2O3 (alumina). Single-crystalline Cr2−xAlxO3 thin films with (0001) surface orientation and varying stoichiometry have been grown by sputter codeposition in the concentration range between x = 0 and x = 0.6. For these samples, we find the corundum crystal structure, the antiferromagnetic ordering, and the boundary magnetization to be preserved. We also find that the critical temperature TN can be tuned by alloying with α-Al2O3, using the BM as a probe to study the magnetic phase transition. Furthermore, we were able to evaluate the critical exponent and the absolute BM values for different samples. Both properties corroborate that the observed magnetic signals originate from the BM rather than the bulk of the samples.
2015-06-02T07:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/78
https://digitalcommons.unl.edu/context/physicsbinek/article/1078/viewcontent/PhysRevB.91.214403.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
boundary magnetization
magnetoelectric
thin films
oai:digitalcommons.unl.edu:physicsbinek-1080
2016-05-24T17:48:33Z
publication:mrsecfacpubs
publication:physicsresearch
publication:physics
publication:physicsbinek
publication:materialsresearchscieeng
Giant temperature dependence of the spin reversal field in magnetoelectric chromia
Fallarino, Lorenzo
Berger, Andreas
Binek, Christian
Magnetic field-induced reversal of surface spin polarization for the magnetoelectric antiferromagnet chromia is studied via magnetometry in (0001)-textured thin films of various thicknesses. Reversal solely by magnetic means has been experimentally evidenced in sufficiently thin films. It sets the field-response of chromia films apart from bulk behavior, where switching between time-reversed single domain states requires the simultaneous presence of electric and magnetic fields. In our detailed experiments, we furthermore observe a giant sensitivity of the coercive field on temperature, thus, indicating the potential of magnetoelectric antiferromagnets as promising candidates for energy assisted magnetic recording media.
2014-01-13T08:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/82
https://digitalcommons.unl.edu/context/physicsbinek/article/1080/viewcontent/1.4861780.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
chromia
thin films
spin polarization
oai:digitalcommons.unl.edu:physicsbinek-1079
2016-05-24T17:41:00Z
publication:physicsresearch
publication:physics
publication:physicsbinek
Spin relaxation time dependence on optical pumping intensity in GaAs:Mn
Burobina, V.
Binek, Christian
We analyze the dependence of electron spin relaxation time on optical pumping intensity in a partially compensated acceptor semiconductor GaAs:Mn using analytic solutions for the kinetic equations of the charge carrier concentrations. Our results are applied to previous experimental data of spin-relaxation time vs. excitation power for magnetic concentrations of approximately 1017 cm-3 . The agreement of our analytic solutions with the experimental data supports the mechanism of the earlier-reported atypically long electron-spin relaxation time in the magnetic semiconductor.
2014-04-30T07:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/83
https://digitalcommons.unl.edu/context/physicsbinek/article/1079/viewcontent/1.4874218.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
spin relaxation
GaAs:Mn
oai:digitalcommons.unl.edu:physicsbinek-1082
2016-05-24T17:58:51Z
publication:physicsresearch
publication:physics
publication:physicsbinek
Near-room-temperature refrigeration through voltage-controlled entropy change in multiferroics
Binek, Christian
Burobina, V.
Composite materials with large magnetoelectric effect are proposed for application in advanced near-room-temperature refrigeration. The key innovation rests on utilizing the magnetocaloric effect in zero applied magnetic fields. This approach promises sizable isothermal entropy change and virtually temperature-independent refrigerant capacity through pure voltage-control. It is in sharp contrast with the conventional method of exploiting the magnetocaloric effect through applied magnetic fields. We outline the thermodynamics and estimate an isothermal entropy change specifically for the La0.7Sr0.3MnO3/Pb(Mg1/3Nb2/3)O3-PbTiO3(001) two-phase composite material. Finally, we propose structural variations of two-phase composites, which help in overcoming the challenging task of producing nanostructured material in macroscopic quantities.
2013-01-25T08:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/80
https://digitalcommons.unl.edu/context/physicsbinek/article/1082/viewcontent/1.4788690.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
voltage-controlled
multiferroics
oai:digitalcommons.unl.edu:physicsbinek-1081
2016-05-24T17:53:20Z
publication:mrsecfacpubs
publication:physicsresearch
publication:physics
publication:physicsbinek
publication:materialsresearchscieeng
Electric Control of Exchange Bias Training
Echtenkamp, W.
Binek, Christian
Voltage-controlled exchange bias training and tunability are introduced. Isothermal voltage pulses are used to reverse the antiferromagnetic order parameter of magnetoelectric Cr2O3, and thus continuously tune the exchange bias of an adjacent CoPd film. Voltage-controlled exchange bias training is initialized by tuning the antiferromagnetic interface into a nonequilibrium state incommensurate with the underlying bulk. Interpretation of these hitherto unreported effects contributes to new understanding in electrically controlled magnetism
2013-10-31T07:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/81
https://digitalcommons.unl.edu/context/physicsbinek/article/1081/viewcontent/PhysRevLett.111.187204.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
exchange bias
voltage-controlled
Cr2O3
oai:digitalcommons.unl.edu:physicsbinek-1083
2016-05-24T20:41:36Z
publication:mrsecfacpubs
publication:physicsresearch
publication:physicstsymbal
publication:physics
publication:physicsbinek
publication:materialsresearchscieeng
Magnetic nanoparticles: recent advances in synthesis, self-assembly and applications
Singamaneni, Srikanth
Bliznyuk, V.
Binek, Christian
Tsymbal, Evgeny Y.
Nanostructured magnetic materials have a variety of promising applications spreading from nano-scale electronic devices, sensors and high-density data storage media to controlled drug delivery and cancer diagnostics/treatment systems. Magnetic nanoparticles offer the most natural and elegant way for fabrication of such (multi-) functional materials. In this review, we briefly summarize the recent progress in the synthesis of magnetic nanoparticles (which now can be done with precise control over the size and surface chemistry), and nanoscale interactions leading to their self-assembly into 1D, 2D or 3D aggregates. Various approaches to self-organization, directed-, or template-assisted assembly of these nanostructures are discussed with the special emphasis on magnetic-field enabled interactions. We also discuss new physical phenomena associated with magnetic coupling between nanoparticles and their interaction with a substrate and the characterization of the physical properties at the nanoscale using various experimental techniques (including scanning quantum interferometry (SQUID) and magnetic force microscopy). Applications of magnetic nanoparticle assemblies in data storage, spintronics, drug delivery, cancer therapy, and prospective applications such as adaptive materials and multifunctional reconfigurable materials are also highlighted.
2011-06-20T07:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/84
https://digitalcommons.unl.edu/context/physicsbinek/article/1083/viewcontent/c1jm11845e.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Magnetic nanoparticles
oai:digitalcommons.unl.edu:physicsbinek-1084
2016-05-26T14:49:41Z
publication:mrsecfacpubs
publication:physicsresearch
publication:physics
publication:physicsbinek
publication:materialsresearchscieeng
Dispersion of Electric-Field-Induced Faraday Effect in Magnetoelectric Cr2O3
Wang, J.
Binek, Christian
The frequency dependence of the electric-field-induced magneto-optical Faraday effect is investigated in the magnetoelectric antiferromagnet chromia. Two electrically induced Faraday signals superimpose in proportion to the linear magnetoelectric susceptibility α and the antiferromagnetic order parameter η. The relative strength of these contributions is determined by the frequency of the probing light and can be tuned between extreme characteristics following the temperature dependence of α or η. The frequency dependence is analyzed in terms of electric dipole transitions of perturbed Cr3+ crystal-field states. The results allow us to measure voltage-controlled selection, isothermal switching, and temperature dependence of η in a tabletop setup. The voltage-specific Faraday rotation is independent of the sample thickness, making the method scalable and versatile down to the limit of dielectric breakdown.
2016-03-30T07:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/85
https://digitalcommons.unl.edu/context/physicsbinek/article/1084/viewcontent/PhysRevApplied.5.031001.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Cr2O3
Faraday effect
chromia
magnetoelectric
Condensed Matter Physics
oai:digitalcommons.unl.edu:physicsbinek-1086
2018-10-30T16:17:02Z
publication:mrsecfacpubs
publication:physicsresearch
publication:physics
publication:physicsbinek
publication:materialsresearchscieeng
Elastic properties of superconductors and materials with weakly correlated spins
Binek, Christian
It is shown that in the ergodic regime, the temperature dependence of Young’s modulus is solely determined by the magnetic properties of a material. For the large class of materials with paramagnetic or diamagnetic response, simple functional forms of the temperature derivative of Young’s modulus are derived and compared with experimental data and empirical results. Superconducting materials in the Meissner phase are ideal diamagnets. As such, they display remarkable elastic properties. Constant diamagnetic susceptibility gives rise to a temperature independent elastic modulus for ceramic and single crystalline superconductors alike. The thermodynamic approach established in this report, paves the way to tailor elastic material parameters through the design of magnetic properties.
2017-07-01T07:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/86
https://digitalcommons.unl.edu/context/physicsbinek/article/1086/viewcontent/Binek_SR_2017_Elastic_properties_of.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
Atomic, Molecular and Optical Physics
Engineering Physics
Materials Science and Engineering
Nanoscience and Nanotechnology
Physical Sciences and Mathematics
Physics
oai:digitalcommons.unl.edu:physicsbinek-1088
2018-10-30T16:16:12Z
publication:mrsecfacpubs
publication:physicsresearch
publication:physics
publication:physicsbinek
publication:materialsresearchscieeng
Dielectric properties of thin Cr2O3 films grown on elemental and oxide metallic substrates
Mahmood, Ather
Street, Mike
Echtenkamp, Will
Kwan, Chun Pui
Bird, Jonathan P.
Binek, Christian
In an attempt to optimize leakage characteristics of α-Cr2O3 thin films, its dielectric properties were investigated at local and macroscopic scale. The films were grown on Pd(111), Pt(111), and V2O3 (0001), supported on Al2O3 substrate. The local conductivity was measured by conductive atomic force microscopy mapping of Cr2O3 surfaces, which revealed the nature of defects that formed conducting paths with the bottom Pd or Pt layer. A strong correlation was found between these electrical defects and the grain boundaries revealed in the corresponding topographic scans. In comparison, the Cr2O3 film on V2O3 exhibited no leakage paths at similar tip bias value. Electrical resistance measurements through e-beam patterned top electrodes confirmed the resistivity mismatch between the films grown on different electrodes. The x-ray analysis attributes this difference to the twin free Cr2O3 growth on V2O3 seeding.
2018-04-02T07:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/87
https://digitalcommons.unl.edu/context/physicsbinek/article/1088/viewcontent/Binek_2_PhysRevMaterials.2.044401.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
thin films
dielectric
oxides
Condensed Matter Physics
oai:digitalcommons.unl.edu:physicsbinek-1087
2018-10-30T16:14:59Z
publication:mrsecfacpubs
publication:physicsresearch
publication:physics
publication:physicsbinek
publication:materialsresearchscieeng
Tuning the Effective Anisotropy in a Voltage-Susceptible Exchange-Bias Heterosystem
Echtenkamp, Will
Street, Mike
Mahmood, Ather
Binek, Christian
Voltage- and temperature-tuned ferromagnetic hysteresis is investigated by a superconducting quantum-interference device and Kerr magnetometry in a thin-film heterostructure of a perpendicular anisotropic Co/Pd ferromagnet exchange coupled to the magnetoelectric antiferromagnet Cr2O3. An abrupt disappearance of exchange bias with a simultaneous more than twofold increase in coercivity is observed and interpreted as a competition between the effective anisotropy of Cr2O3 and the exchange-coupling energy between boundary magnetization and the adjacent ferromagnet. The effective anisotropy energy is given by the intrinsic anisotropy energy density multiplied by the effective volume separated from the bulk through a horizontal antiferromagnetic domain boundary. Kerr measurements show that the anisotropy of the interfacial Cr2O3 can be tuned isothermally and in the absence of an external magnetic field by application of an electric field. A generalized Meiklejohn-Bean model accounts for the change in exchange bias and coercivity as well as the asymmetric evolution of the hysteresis loop. In support of this model, the reversal of the boundary magnetization is experimentally confirmed as a contribution to the magnetic hysteresis loop
2017-03-23T07:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/88
https://digitalcommons.unl.edu/context/physicsbinek/article/1087/viewcontent/Binek_PhysRevApplied.7.034015.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
exchange bias
Kerr magnetometry
anisotropy
Condensed Matter Physics
oai:digitalcommons.unl.edu:physicsbinek-1089
2019-11-08T13:51:57Z
publication:mrsecfacpubs
publication:physicsresearch
publication:physics
publication:physicsbinek
publication:materialsresearchscieeng
Electromagnon excitation in cupric oxide measured by Fabry-Pérot enhanced terahertz Mueller matrix ellipsometry
Knight, Sean
Prabhakaran, Dharmalingam
Binek, Christian
Schubert, Mathias
Here we present the use of Fabry-Pérot enhanced terahertz (THz) Mueller matrix ellipsometry to measure an electromagnon excitation in monoclinic cupric oxide (CuO). As a magnetically induced ferroelectric multiferroic, CuO exhibits coupling between electric and magnetic order. This gives rise to special quasiparticle excitations at THz frequencies called electromagnons. In order to measure the electromagnons in CuO, we exploit single-crystal CuO as a THz Fabry-Pérot cavity to resonantly enhance the excitation’s signature. This enhancement technique enables the complex index of refraction to be extracted. We observe a peak in the absorption coefficient near 0.705 THz and 215 K, which corresponds to the electromagnon excitation. This absorption peak is observed along only one major polarizability axis in the monoclinic a–c plane. We show the excitation can be represented using the Lorentz oscillator model, and discuss how these Lorentz parameters evolve with temperature. Our findings are in excellent agreement with previous characterizations by THz time-domain spectroscopy (THz-TDS), which demonstrates the validity of this enhancement technique.
2019-02-04T08:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/91
https://digitalcommons.unl.edu/context/physicsbinek/article/1089/viewcontent/scientific_report_2019_Binek_Schubert_s41598_018_37639_8.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
ellipsometry
electromagnon
excitation
Mueller matrix
Condensed Matter Physics
Electronic Devices and Semiconductor Manufacturing
oai:digitalcommons.unl.edu:physicsbinek-1090
2019-11-22T14:57:05Z
publication:mrsecfacpubs
publication:physicsresearch
publication:physics
publication:physicsbinek
publication:materialsresearchscieeng
Voltage controlled magnetism in Cr2O3 based all-thin-film systems
Wang, Junlei
Echtenkamp, Will
Mahmood, Ather
Binek, Christian
Voltage-control of exchange biases through active selection of distinct domain states of the magnetoelectric and antiferromagnetic pinning layer is demonstrated for Cr2O3/CoPd heterostructures. Progress and obstacles towards an isothermal switching of exchange bias are discussed. An alternative approach avoiding exchange bias for voltage-controlled memory exploits boundary magnetization at the surface of Cr2O3 as voltage-controlled state variable. We demonstrate readout and switching of boundary magnetization in ultra-thin Cr2O3/Pt Hall bar devices where reversal of boundary magnetization is achieved via magnetoelectric annealing with simultaneously applied ±0.5 V and 400 mT electric and magnetic fields.
2019-05-31T07:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/90
https://digitalcommons.unl.edu/context/physicsbinek/article/1090/viewcontent/JMMM_2019_1_s2.0_S0304885319304056_main.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
voltage controlled magnetism
Cr2O3
thin films
Condensed Matter Physics
oai:digitalcommons.unl.edu:physicsbinek-1091
2019-11-22T14:56:31Z
publication:physicsresearch
publication:physics
publication:physicsbinek
Space-charge limited conduction in epitaxial chromia films grown on elemental and oxide-based metallic substrates
Kwan, C.-P.
Street, Mike
Mahmood, Ather
Echtenkamp, Will
Randle, M.
He, K.
Nathawat, J.
Arabchigavkani, N.
Barut, B.
Yin, S.
Dixit, R.
Singisetti, Uttam
Binek, Christian
Bird, J. P.
We study temperature dependent (200 – 400 K) dielectric current leakage in high-quality, epitaxial chromia films, synthesized on various conductive substrates (Pd, Pt and V2O3). We find that trap-assisted space-charge limited conduction is the dominant source of electrical leakage in the films, and that the density and distribution of charge traps within them is strongly dependent upon the choice of the underlying substrate. Pd-based chromia is found to exhibit leakage consistent with the presence of deep, discrete traps, a characteristic that is related to the known properties of twinning defects in the material. The Pt- and V2O3-based films, in contrast, show behavior typical of insulators with shallow, exponentially-distributed traps. The highest resistivity is obtained for chromia fabricated on V2O3substrates, consistent with a lower total trap density in these films. Our studies suggest that chromia thin films formed on V2O3 substrates are a promising candidate for next-generation spintronics,
2019-05-21T07:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsbinek/89
https://digitalcommons.unl.edu/context/physicsbinek/article/1091/viewcontent/aip_advances.pdf
Christian Binek Publications
DigitalCommons@University of Nebraska - Lincoln
epitaxial chromia films
oxides
thin films
band gap
spintronics
Condensed Matter Physics
oai:digitalcommons.unl.edu:physicsdowben-1274
2020-03-23T16:45:58Z
publication:mrsecfacpubs
publication:physicsresearch
publication:physicsdowben
publication:physicshong
publication:physics
publication:physicsbinek
publication:materialsresearchscieeng
Towards a Strong Spin–Orbit Coupling Magnetoelectric Transistor
Dowben, Peter
Binek, Christian
Zhang, Kai
Wang, Lu
Mei, Wai-Ning
Bird, Jonathan P.
Singisetti, Uttam
Hong, Xia
Wang, Kang L.
Nikonov, Dmitri
Here, we outline magnetoelectric (ME) device concepts based on the voltage control of the interface magnetism of an ME antiferromagnet gate dielectric formed on a very thin semiconductor channel with large spin–orbit coupling (SOC). The emphasis of the ME spin field-effect transistors (ME spin FET) is on an antiferromagnet spin–orbit read logic device and a ME spin-FET multiplexer. Both spin-FET schemes exploit the strong SOC in the semiconducting channel materials but remain dependent on the voltage-induced switching of an ME, so that the switching time is limited only by the switching dynamics of the ME. The induced exchange field spin polarizes the channel material, breaks time-reversal symmetry, and results in the preferential charge transport direction, due to the spin–orbit-driven spin-momentum locking. These devices could provide reliable room temperature operation with large on/off ratios, well beyond what can be achieved using magnetic tunnel junctions. All of the proposed device spintronic functionalities without the need to switch a ferromagnet, yielding a faster writing speed (~10 ps) at a lower cost in energy (~10 aJ), excellent temperature stability (operational up to 400 K or above), and requiring far fewer device elements (transistor equivalents) than CMOS.
2018-01-01T08:00:00Z
text
application/pdf
https://digitalcommons.unl.edu/physicsdowben/274
https://digitalcommons.unl.edu/context/physicsdowben/article/1274/viewcontent/Dowben_IEEEJESSCDC_2018_Towards_a_Strong_Spin__MS_FINAL.pdf
https://digitalcommons.unl.edu/context/physicsdowben/article/1274/filename/0/type/additional/viewcontent/Dowben_2018_IEEE_supplemental.zip
Peter Dowben Publications
DigitalCommons@University of Nebraska - Lincoln
Magnetoelectric (ME) transistor
nonvolatile logic and memory
spin–orbit coupling (SOC)
Atomic, Molecular and Optical Physics
Condensed Matter Physics
Engineering Physics
Other Physics
Physical Sciences and Mathematics
Physics