Magnetic properties and the crystallization of amorphous ${\mathrm{Fe}}_{75.4}$${\mathrm{B}}_{14.2}$${\mathrm{Si}}_{10.4}$

The amorphous state of ferromagnetic ${\mathrm{Fe}}_{75.4}$ ${\mathrm{B}}_{14.2}$ ${\mathrm{Si}}_{10.4}$ and its crystalline phases after crystallization have been studied by Mössbauer spectroscopy and magnetic-moment measurements. The average hyperfine field $H_{\mathrm{hf}}\mathrm{}\left(T\right)\mathrm{}$ of the amorphous state shows a temperature dependence of $\frac{\left[H_{\mathrm{hf}}\mathrm{}\right(T)-H_{\mathrm{hf}}\mathrm{}(0\left)\right]}{H_{\mathrm{hf}}\mathrm{}\left(0\right)=-0.30\mathrm{}{\left(\frac{T}{T_c}\right)}^{\frac{3}{2}}-0.16\mathrm{}{\left(\frac{T}{T_c}\right)}^{\frac{5}{2}}}$ for $\frac{T}{T_c}<0.7\mathrm{}$, indicative of spin-wave excitation. The quadrupole splitting just above $T_c$ is 0.46 mm/s, whereas the average quadrupole shift below $T_c$ is zero. The Curie and crystallization temperatures are determined to be $T_c=701\mathrm{}$ K and $T_x=827\mathrm{}$ K, respectively, for a heating rate of 11 K/min. The final products of crystallization are found to be ${\mathrm{Fe}}_2$B and a Fe-18.1 at.% Si alloy. The saturation magnetic moment of the amorphous state extrapolated to 0 K is found to be $\frac{2.05{\mu }_B}{\mathrm{Fe}}$ atom. The magnetization of the amorphous phase decreases more rapidly with reduced temperature than those of crystalline ferromagnets. This kind of rapid decrease can be described in terms of either a distribution of exchange interactions in the amorphous phase or high metalloid contents.