Fe57Mössbauer effect and magnetic properties in amorphous Fe-based alloys

Abstract

The magnetic properties of amorphous ${\mathrm{Mg}}_{1-x}{\mathrm{Fe}}_x$ alloys were studied by means of magnetization measurements and the ${}_{}{}^{57}{}_{}{}^{}\mathrm{Fe}$ Mössbauer effect. It was found that the apparent decrease with $x$ of the Fe moment derived from magnetization measurements is due to deviations from a collinear ferromagnetic moment arrangement. The average effective hyperfine field $〈H_{\mathrm{eff}}〉$ observed in amorphous $A_{1-x}{\mathrm{Fe}}_x$ alloys when $A$ = Mg and Th was compared with literature data on amorphous alloys with $A$ = Zr, Y, La, and Sn. A correlation was found to exist between $〈H_{\mathrm{eff}}〉$ and the corresponding values of the formation enthalpies. These results are in accordance with a model proposed earlier, in which the magnetic properties of amorphous alloys are largely determined by the presence of compositional short-range order. Sign and magnitude of the formation enthalpies are a measure of the nature and the degree of this compositional short-range order. In amorphous $A_{1-x}{\mathrm{Fe}}_x$ alloys with $A$ = Mg, Th, and Ge the room-temperature ${}_{}{}^{57}{}_{}{}^{}\mathrm{Fe}$ isomer shift was studied. Together with literature data on amorphous alloys with $A$ = Y, Mg, Sn, Ge, and Sb the isomer shifts were analyzed in terms of a model proposed by Miedema and van der Woude.