Activation entropy, activation energy, and magnetic viscosity

Authors

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

Date of this Version

April 1999

Comments

Published in Journal of Applied Physics, 85:8 (April 15, 1999), 5069-5071. DOI: 10.1063/1.370093
Copyright © 1999 The American Institute of Physics. Used by permission.
Journal website = http://jap.aip.org/

Abstract

Starting from an exact quantum-statistical description, the influence of the shape of the energy landscape on the magnetic viscosity is investigated. Magnetic phase-space analysis based on Kramers’ escape-rate theory of chemical reaction kinetics theory shows that the activation entropy associated with thermally activated hopping modifies the magnetic viscosity by reducing the attempt-frequency prefactor compared to an earlier prediction by Brown [W. F. Brown, Phys. Rev. 130, 1677 (1963)]. Energetic contributions are analyzed in terms of a model applicable to a range of coherent and noncoherent magnetization processes, and in the long-time limit deviations from the linear logarithmic magnetic-viscosity law are found.