Detailed Investigation of the Magnetization of an Amorphous Ferromagnet Fe₈₃B₁₇

Abstract

We have carried out precise measurements of the magnetization on an amorphous metallic ferromagnet Fe₈₃B₁₇ from 4.2 K to 340 K in a high field of 5.03 T. Detailed analysis of the observed data shows that the magnetization does not obey a simple spin wave T^3⁄2 law but follows a sum of the renormalized spin wave term and the Stoner-type contribution varying as T² rather than e^−Δ⁄k_BT. The spin wave stiffness constant is expressed as D=D₀(1−D₂T^5⁄2) with D₀=120±5 meV Ų and D₂=(2.0±0.5)×10⁻⁸ K^−5⁄2, which is roughly consistent with that determined directly from neutron scattering. This suggests no existence of the well-known anomaly of the spin wave stiffness constant reported in earlier measurements. We discuss behavior of the magnetization at finite temperatures in terms of the local magnetic moment.