Entropy localization in magnetic compounds and thin-film nanostructures

Authors

Ralph Skomski, University of Nebraska-LincolnFollow
Christian Binek, University of Nebraska-LincolnFollow
Steven A. Michalski, University of Nebraska-LincolnFollow
Tathagata Mukherjee, University of Nebraska-LincolnFollow
Axel Enders, University of Nebraska-LincolnFollow
David J. Sellmyer, University of Nebraska-LincolnFollow

Date of this Version

2010

Comments

Published in JOURNAL OF APPLIED PHYSICS 107, 09A922 (2010). Copyright © 2010 American Institute of Physics. Used by permission.

Abstract

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.