Local-environment model for the hyperfine interactions inFe3−xNixSi

X-ray, magnetization, spin-echo NMR, and Mössbauer techniques have been used to study the local magnetic-moment formation and corresponding hyperfine-field interactions in ${\mathrm{Fe}}_{3-x}{\mathrm{Ni}}_x\mathrm{Si}$ for $0<~x<~1$. The x-ray measurements indicate that a single phase having the fcc $D{O}_3$-type structure is formed for $x<~0.9$ with a slight increase in the lattice constant as Ni is added. The alloys are ferromagnetic throughout the entire composition range studied with a saturation magnetic moment that decreases from $4.8{\mu }_B$ per formula unit for $x=0\mathrm{} \mathrm{to} 4.0{\mu }_B$ per formula unit for $x=0.9\mathrm{}$. The NMR measurements show that Ni replaces Fe in the ($A,C$) sites for $0<~x<~0.9$ and consequently a local environment model relating the hyperfine fields with the magnetic moments previously developed for related systems can be applied. In this model the Ni moment remains approximately constant at $0.9{\mu }_B$ for $x<~0.6$. The $\mathrm{Fe}\mathrm{}\left(B\right)\mathrm{}$ moment increases from $2.2{\mu }_B$ for no Ni 1NN to $3.0{\mu }_B$ for 1 Ni 1NN and then decreases gradually to $2.7{\mu }_B$ for 4 Ni first-nearest neighbors (1NN). When one uses this model for the magnetic-moment formation, a subdivision of the observed internal fields into contributions arising from the $4s$ spin polarization transferred from neighboring moments and the polarization resulting from the on-site moments is obtained. The on-site contribution for Ni ($H_{\mathrm{cp}}+H_s$) was found to be $+120\mathrm{}\frac{\mathrm{kOe}}{{\mu }_B}$ while that for $\mathrm{Fe}\mathrm{}\left(B\right)\mathrm{}$ was $-93.18\mathrm{}\frac{\mathrm{kOe}}{{\mu }_B}$.