Magneto-Optical Properties of Amorphous Rare-Earth Transition-Metal Alloy Films at Low Temperatures

The Kerr rotation angle (θ
_k
) and sublattice magnetization (M
_TM
) of GdFeCo film were studied. θ
_k
could be increased by adding Co to GdFe film to a concentration of approximately 30 percent. Above that point, θ
_k
began to decrease. θ
_k
was essentially proportional to M
_TM
through Co concentrations of 50 percent, but above 30 percent, μ
_k
decreased more rapidly than M
_TM
.