High-field susceptibility and the spin-wave spectrum of Fe40Ni40P14B6-alloys

Abstract In amorphous Fe 40 Ni 40 P 14 B 6 -alloys, we have investigated the temperature and the field dependence of the law of approach to ferromagnetic saturation. Bloch's T 3 2 -law was found to be valid below 1 2 T c and the parasusceptibility followed an H - 1 2 -law. The spin-wave stiffness constant, D , of the spin-wave dispersion law, ϵ k = D k 2 , was found to be D = 78 meV A 2 . Furthermore, an A/H 2 -term in the susceptibility could be attributed to inhomogeneities in the microstructure of the amorphous state.