Neutron scattering study of spin waves in the amorphous metallic ferromagnet (Fe93Mo7)80B10P10

Low-angle inelastic-neutron-scattering experiments were performed on an amorphous ferromagnet of composition (Fe93Mo7)80B10P10 with Tc=450 K. Well-defined spin waves were observed over the entire range of momentum transfer for which the scattering triangle could be closed (q≤0.25 -1). The results were consistent with a normal ferromagnetic dispersion relation hω(q)=Δ+Dq2+Eq4+..., where the gap Δ can be largely accounted for by demagnetization effects. Low-temperature magnetization measurements were performed and fit to the relation M(T)=M0 (1-BT32-CT52). The measured long-wavelength spin waves account for only 70% of the density of magnon states necessary to explain M(T). For temperatures below 300 K, the mean spin-wave energies are well represented by the relation ω(q, T)=ω(q,0)[1-0. 612(TTc)52]. © 1977 The American Physical Society.