  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 Imry-Ma domains 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 the spatial pattern of the
amplitude of spin oscillations exhibits maxima corresponding to the
oscillations of resonant magnetic domains. The dependence of the peak
absorption frequency on the ratio of the magnitude of per-spin random
anisotropy to the strength of the ferromagnetic exchange agrees with the
scaling derived from the Imry-Ma argument. The effect noticeably increases in
low-dimensional systems, suggesting that materials comprised of microscopic
amorphous leaves and wires can be promising candidates for enhanced microwave
absorption.
