Hysteresis and relaxation in granular permanent magnets

Authors

Ralph Skomski, University of Nebraska-LincolnFollow
Balamurugan Balamurugan, University of Nebraska-LincolnFollow
Thomas A. George, University of Nebraska-LincolnFollow
Mircea Chipara, University of Texas Pan AmericanFollow
Xiao-Hui Wei, University of Nebraska-Lincoln
Jeffrey E. Shield, University of Nebraska-LincolnFollow
David J. Sellmyer, NCMNFollow

Document Type

Article

Date of this Version

2012

Citation

JOURNAL OF APPLIED PHYSICS 111, 07B507 (2012). doi:10.1063/1.3672845

Comments

Copyright © 2012 American Institute of Physics. Used by Permission.

Abstract

Some nontrivial aspects of the magnetic and structural characterization of hard-magnetic nanoparticles are investigated. Dilute ensembles are well-described by mean-field theory, although there is an asymmetry between exchange and magnetostatic interaction fields. Corrections to the mean-field approximation are caused by cooperative effects and have the character of Onsager reaction fields, which are much stronger in micromagnetism than in atomic-scale magnetism. The slow dynamics of zero-field-cooled (ZFC) magnetization curves is strongly affected by the particles0 magnetic anisotropy, which reduces the corresponding energy-barrier height from 25 to 19.1 k_BT.