Neutron Scattering Study of Spin Waves in the Amorphous Ferromagnet (Fe0.3Ni0.7)0.75P0.16B0.06Al0.03

Abstract

The neutron inelastic scattering technique has been used to measure the collective magnetic excitation spectrum in the ferromagnetic (${\mathrm{T}}_{\mathrm{C}}\text{∼255}\mathrm{K}$ ) metallic glass $({\mathrm{Fe}}_{\text{0.3}}{\mathrm{Ni}}_{\text{0.7}}{)}_{\text{0.75}}{\mathrm{P}}_{\text{0.16}}{\mathrm{B}}_{\text{0.06}}{\mathrm{Al}}_{\text{0.03}}$ . In this system only the iron atoms appear to be magnetic, and the observation of relatively well‐defined spin waves is striking in comparison with other amorphous systems where the spin waves rapidly broaden with decreasing iron concentration. The spin waves obey the conventional quadratic dispersion relation ${\mathrm{E}}_{\mathrm{sw}}={\mathrm{DQ}}^2$ , with $\mathrm{D}\text{=35}\mathrm{meV}{\mathrm{‐\AA }}^2$ . Contributions from fourth and higher order terms in the dispersion relation are not in evidence for wave vectors in the region investigated ($\mathrm{Q}{\text{\hspace{0.17em}≲\hspace{0.17em}0.25\hspace{0.17em}Å}}^{\text{−1}}$ ).