Irreversible magnetization in some ferromagnetic insulators

Abstract

A unified description of the nonlinear ferromagnetic behavior under applied field has been proposed. A relaxation of intrinsic magnetization after a sudden temperature change and elementary irreversible magnetization processes in ‘uniform’ ferromagnetic insulators were discussed. The treatment is based on the thermodynamic potential evaluated on a nonequilibrium state. By deriving the entropy production from this thermodynamic potential and employing the standard technique in the Prigogine-de Groot theory in nonequilibrium thermodynamics, the changing rate of intrinsic magnetization or equations of motion for individual irreversible magnetization processes were obtained. Necessarily, the equations of wall motion or magnetization rotation are compatible with the static magnetization curve or hysteresis loop that are obtained by minimizing the same thermodynamic potential. The magnetothermal effect associated with irreversible change was formulated.