  Magnetic order and microwave absorption in amorphous ferromagnets and
materials sintered from nanoscale ferromagnetic grains are investigated
analytically and numerically within the random-anisotropy model. We show that a
scaling argument specific to static randomness allows one to make conclusions
about the behavior of a large system with a weak disorder by studying a smaller
system with a strong disorder. The breakdown of the scaling on increasing the
strength of the magnetic anisotropy and/or the size of the grain separates two
distinct regimes in magnetic ordering and frequency dependence of the absorbed
microwave power. Analytical results are confirmed by numerical experiments on
spin lattices containing up to ten million spins. Our findings should help
design materials with desired magnetic and microwave properties. The method can
be extended to other systems with quenched randomness.
