Effects of random field interactions in amorphous rare earth alloys

Recent neutron small angle scattering studies have shown that amorphous alloys of non S-state rare earth elements with Fe are not ferrimagnetic as inferred from magnetization data, but rather exhibit a spin-glass type of order. The data show no divergence in the spin correlation length below Tc, and the gradual evolution of the scattering lineshape from Lorentzian to a Lorentzian plus Lorentzian squared form appropriate for a system in which random fields destroy the long range order. SANS data taken in applied fields indicate the formation of an infinite cluster in low fields which is responsible for the ferrimagnetic magnetization response and which co-exists with increasingly smaller residual clusters.