Mössbauer-spectroscopy study of amorphous Fe-Ge alloys

A Mössbauer-spectroscopy study of amorphous Fe_xGe_1-x, with 0.11<x<0.72, was performed to measure the hyperfine-field parameters at 22 and 295 K. The distributions of quadrupole splitting suggest that for x<0.2, the structure of the alloys is homogeneous and Fe atoms probably occupy the interstices of the Ge tetrahedral structure. For concentrations of x>0.4, however, hyperfine-field parameters seem to indicate that the alloys contain a mixture of short-range-order phases, with the average hyperfine magnetic field rising sharply with concentration. The resulting analysis of isomer shift, in terms of the model of Miedema and Van der Woude [Physica B 100, 145 (1980)], shows the Fe magnetic moment to be strongly influenced by hybridization and intra-atomic charge redistribution.