Ultrahard magnetic nanostructures

Authors

P. K. Sahota, University of Nebraska-Lincoln
Yi Liu, University of Nebraska-LincolnFollow
Ralph Skomski, University of Nebraska-LincolnFollow
Priyanka Manchanda, LNM Institute of Information TechnologyFollow
R. Zhang, University of Nebraska-Lincoln
M. Franchin, University of Southampton, Southampton
H. Fangohr, University of Southampton, Southampton
George C. Hadjipanayis, University of DelawareFollow
Arti Kashyap, LNM Institute of Information Technology, Jaipur, Rajasthan, IndiaFollow
David J. Sellmyer, University of Nebraska-LincolnFollow

Date of this Version

2012

Citation

JOURNAL OF APPLIED PHYSICS 111, 07E345 (2012); doi:10.1063/1.3679453

Comments

Copyright 2012 American Institute of Physics

Abstract

The performance of hard-magnetic nanostructures is investigated by analyzing the size and geometry dependence of thin-film hysteresis loops. Compared to bulk magnets, weight and volume are much less important, but we find that the energy product remains the main figure of merit down to very small features sizes. However, hysteresis loops are much easier to control on small length scales, as epitomized by Fe-Co-Pt thin films with magnetizations of up to 1.78 T and coercivities of up to 2.52 T. Our numerical and analytical calculations show that the feature size and geometry have a big effect on the hysteresis loop. Layered soft regions, especially if they have a free surface, are more harmful to coercivity and energy product than spherical inclusions. In hard-soft nanocomposites, an additional complication is provided by the physical properties of the hard phases. For a given soft phase, the performance of a hard-soft composite is determined by the parameter (M_s - M_h)/K_h.