Equivalence of sweep-rate and magnetic-viscosity dynamics

Authors

Ralph Skomski, University of Nebraska-LincolnFollow
Roger D. Kirby, University of Nebraska-LincolnFollow
David J. Sellmyer, University of Nebraska-LincolnFollow

Document Type

Article

Date of this Version

May 2003

Comments

Published in Journal of Applied Physics, 93:10 (2003), 6820-6822. DOI: 10.1063/1.1557276
Copyright © 2003 The American Institute of Physics. Used by permission.
Journal website = http://jap.aip.org/

Abstract

The irreversible response of magnetic materials to magnetic fields of arbitrary time dependence is investigated by a master-equation approach. The magnetization reversal is expressed in terms of renormalized magnetization modes, and the resulting set of two-level master equations is solved by direct integration. The theory applies not only to linear energy-barrier laws but also to the physically more reasonable case where the activation energy is a nonlinear function of the applied field. Particular emphasis is on the relation between sweep-rate and magnetic-viscosity dynamics. Other regimes, such as oscillating magnetic fields, can be mapped onto sweep-rate dynamics. Magnetic-viscosity and sweep-rate experiments reflect the same fundamental magnetization processes, but energy barriers probed by dynamic experiments are smaller by about 20%.