Double-transition behavior induced by anisotropy

We have studied the effect of anisotropy on transition behavior in Gd-transition-metal glasses. Anisotropy is induced in a controlled fashion by the formation of alloys with anisotropic rare-earth metals. For large anisotropy we find paramagnetic-speromagnetic transition behavior as seen by many other workers. In the speromagnetic state the spins are frozen in random direction much like a spin-glass state. For small enough anisotropy we see double-transition behavior that is a sequence of paramagnetic-to-ferromagnetic-to-speromagnetic transitions with decreasing temperature. This behavior is similar to the double-transition behavior seen in many systems where exchange fluctuations are present.