Giant Enhancement of Magnetic Anisotropy in Ultrathin Manganite Films via Nanoscale 1D Periodic Depth Modulation

Authors

Anil Rajapitamahuni, University of Nebraska - LincolnFollow
L. Zhang, University of Nebraska - Lincoln
Mark A. Koten, University of Nebraska-LincolnFollow
V. R. Singh, University of Nebraska-LincolnFollow
John D. Burton, University of Nebraska-LincolnFollow
Evgeny Y. Tsymbal, University of Nebraska-LincolnFollow
Jeffrey E. Shield, University of Nebraska-LincolnFollow
Xia Hong, University of Nebraska–LincolnFollow

Date of this Version

5-6-2016

Citation

PHYSICAL REVIEW LETTERS 116, 187201 (2016). DOI:http://dx.doi.org/10.1103/PhysRevLett.116.187201

Comments

Copyright (c) 2016 American Physical Society. Used by permission.

Abstract

The relatively low magnetocrystalline anisotropy (MCA) in strongly correlated manganites (La,Sr)MnO₃ has been a major hurdle for implementing them in spintronic applications. Here we report an unusual, giant enhancement of in-plane MCA in 6 nm La_0.67Sr_0.33MnO₃ (LSMO) films grown on (001) SrTiO₃ substrates when the top 2 nm is patterned into periodic stripes of 100 or 200 nm width. Planar Hall effect measurements reveal an emergent uniaxial anisotropy superimposed on one of the original biaxial easy axes for unpatterned LSMO along (110) directions, with a 50-fold enhanced anisotropy energy density of 5.6 × 10⁶ erg/cm³ within the nanostripes, comparable to the value for cobalt. The magnitude and direction of the uniaxial anisotropy exclude shape anisotropy and the step edge effect as its origin. High resolution transmission electron microscopy studies reveal a nonequilibrium strain distribution and drastic suppression in the c-axis lattice constant within the nanostructures, which is the driving mechanism for the enhanced uniaxial MCA, as suggested by first-principles density functional calculations.