${\left({\mathrm{Fe}}_{0.25}{\mathrm{Ni}}_{0.75}\right)}_{75}$${\mathrm{B}}_{25}$: A model system to study the local structure in metal-metalloid glasses by means of Mössbauer spectroscopy

High-pressure Mössbauer studies of amorphous and crystaline ${\left({\mathrm{Fe}}_{0.25}{\mathrm{Ni}}_{0.75}\right)}_{75}$ ${\mathrm{B}}_{25}$ at 4.2 K are presented. The similar response of all hyperfine parameters for both the amorphous and crystalline phase with decreasing volume indicates similar local structure in the two phases. The analysis of the pressure dependence of the hyperfine field $B_{\mathrm{eff}}$ at the ${}_{}{}^{57}{}_{}{}^{}\mathrm{Fe}$ nucleus shows, that (i) the magnitude of $B_{\mathrm{eff}}$ in this metal-metalloid glass is mainly determined by the iron-boron (Fe-B) interaction and (ii) the fluctuation in the Fe-B distances is only about 3% compared with about 7.8% in the Fe-Fe distances. The Mössbauer spectrum of the amorphous system in the paramagnetic phase (Curie temperature $T_C=276\mathrm{}$ K) with an external magnetic field of 5 T gives evidence for the occurrence of large spin clusters at 300 K. The pressure dependence of $T_C$ for both phases has been measured with the "thermal scanning" technique and is discussed within the framework of existing theoretical approaches.