We have performed a neutron scattering study of the spin correlations in the amorphous alloys ${\left({\mathrm{Fe}}_{1-x}{\mathrm{Mn}}_x\right)}_{75}{\mathrm{P}}_{16}{\mathrm{B}}_6{\mathrm{Al}}_3$ 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 $Q^{-2.6\mathrm{}}$ power-law decay at low temperatures. We present a simple model for this behavior based on random field effects.

• Received 14 December 1981

DOI:https://doi.org/10.1103/PhysRevB.25.4882