  In the disordered local moment picture, we calculated the magnetization (M)
and magnetic anisotropy energy (MAE) of FePt, CoPt, and MnAl ordered alloys and
body-centered tegragonal FeCo (bct-FeCo) disordered alloy, assuming spatially
fluctuated spin configurations at finite temperatures. All alloys exhibit the
relation K1(T)/K1(0)=(M(T)/M(0))^n with the exponent (n) around 2. This is
consistent with the two-ion anisotropy model, in contrast to the usual
single-ion anisotropy model exhibiting n=3. Because these systems have
different mechanisms of MAE, we suggest that this relation is a general rule
for itinerant electron systems.
