Spin correlations near the ferromagnetic—spin-glass crossover point in amorphous Fe-Mn alloys

Abstract

We have performed a neutron scattering study of the spin correlations in the amorphous alloys ${({\mathrm{Fe}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x})}_{75}{\mathrm{P}}_{16}{\mathrm{B}}_{6}{\mathrm{Al}}_{3}$ with $x$=0.35 and 0.25; the former exhibits short-range spin correlations at all temperatures. The latter displays a paramagnetic-ferromagnetic transition followed by a gradual evolution into a state characterized by ${Q}^{\ensuremath{-}2.6}$ power-law decay at low temperatures. We present a simple model for this behavior based on random field effects.