Integral absorption of microwave power by random-anisotropy magnets

We study analytically, within a continuous field model, and numerically, on lattices containing 10(5) spins, the integral absorption of microwaves by a random-anisotropy magnet, integral d omega P(omega). It scales as D-R(2)/J on the random-anisotropy strength D-R and the strength of the ferromagnetic exchange J in low-anisotropy amorphous magnetic materials. At high anisotropy and in low-anisotropy materials sintered from sufficiently large ferromagnetic grains, the integral power scales linearly on D-R. The maximum bandwidth, combined with the maximum absorption power, is achieved when the amorphous structure factor, or grain size, is of the order of the domain wall thickness in a conventional ferromagnet that is of the order of (J/D-R)(1/2) lattice spacings.