A Mössbauer spectral study of the NdMn6−xFexGe6 solid solutions

The Mössbauer spectra of the NdMn6−xFexGe6 solid solutions, with x = 0.5, 1.0 and 1.5 have been obtained at 4.2, 78 and 295 K. They are analyzed in terms of a binomial distribution of environments for the iron 3g sites. The 78 K weighted average hyperfine fields vary between 14.7 and 15.3 T. The hyperfine field increases with increasing number of iron near neighbours. The isomer shift decreases with increasing x, in agreement with the concomitant unit-cell contraction. The 78 K quadrupole shift of NdMn5.5Fe0.5Ge6 is different from those of NdMn5FeGe6 and NdMn4.5Fe1.5Ge6 and indicates that the iron magnetic moments have a different orientation in the former compound, i.e., they lie in the basal plane of the hexagonal unit cell.