Mössbauer study of amorphous Fe82B12Si6

Abstract

Amorphous ${\mathrm{Fe}}_{82}$ ${\mathrm{B}}_{12}$ ${\mathrm{Si}}_6$ in ribbon form has been investigated over a large temperature range from 2 to 796 K using the Mössbauer technique. The values of the average hyperfine field $H_{\mathrm{hf}}\mathrm{}\left(T\right)\mathrm{}$ show a temperature dependence $\frac{\left[H_{\mathrm{hf}}\mathrm{}\right(T)-H_{\mathrm{hf}}\mathrm{}(0\left)\right]}{H_{\mathrm{hf}}\mathrm{}\left(0\right)\mathrm{}}=-B_{\frac{3}{2}}{\left(\frac{T}{T_F}\right)}^{\frac{3}{2}}-C_{\frac{5}{2}}{\left(\frac{T}{T_F}\right)}^{\frac{5}{2}\dots }$, for $\frac{T}{T_F}<0.8\mathrm{}$, indicative of spin-wave excitation. The values of $B_{\frac{3}{2}}=0.34\mathrm{}\pm 0.05$ and $C_{\frac{5}{2}}=0.21\mathrm{}\pm 0.05$ have been determined. The quadrupole splitting just above $T_F$ is 0.45 mm/s, whereas the average quadrupole shift below $T_F$ is zero. The implication is that the magnetic hyperfine field is randomly oriented with respect to the electric field gradient. A tension experiment indicates that ${\mathrm{Fe}}_{82}$ ${\mathrm{B}}_{12}$ ${\mathrm{Si}}_6$ exhibits positive magnetostriction. This property in combination with thermal expansion is apparently responsible for the in-plane and out-of-plane anisotropy of a clamped sample observed at high and low temperatures, respectively. The Curie and crystallization temperatures are determined to be $T_F=658\mathrm{}$ K and $T_X=780\mathrm{}$ K, respectively.