Absorption of microwaves by random-anisotropy magnets

Abstract

Microscopic model of the interaction of spins with a microwave field in a random-anisotropy magnet has been developed. Numerical results show that microwave absorption occurs in a broad range of frequencies due to the distribution of ferromagnetically correlated regions on sizes and effective anisotropy. That distribution is also responsible for the weak dependence of the absorption on the damping. At a fixed frequency of the ac-field, spin oscillations are localized inside isolated correlated regions. Scaling of the peak absorption frequency agrees with the theory based upon the Imry-Ma argument. The effect of the dimensionality of the system related to microwave absorption by thin amorphous magnetic wires and foils has been studied.