Mössbauer investigations on (Er, P(Fe, A compounds and their nitrides

(Formula presented) Mössbauer studies have been carried out on ((Formula presented)(Formula presented)(Formula presented)(Formula presented) compounds [x=0, 0.4, 0.6, 1.0], ((Formula presented)(Formula presented)(Formula presented)(Formula presented)(Formula presented) [x=0,1,2,3,5,6,8,10] and their nitrides, both in the ferromagnetic and in the paramagnetic phases. Individual hyperfine parameters corresponding to the four crystallographically inequivalent Fe sites have been obtained by analyzing the Mössbauer spectra. The easy magnetization direction, which lies in the basal plane for ((Formula presented)(Formula presented)(Formula presented)(Formula presented) compounds, changes to the axial direction at 18 K, on nitrogenation, which may be due to the increase in the rare-earth sublattice anisotropy. There is an increase in the hyperfine fields at all Fe sites on nitrogenation and the maximum increase in the weighted average hyperfine field is about 40 kOe, which is explained on the basis of 3d band narrowing. The isomer shifts are also found to increase with increasing nitrogen content, which may be due to the reduction in the s-electron density at the nucleus as a result of lattice expansion and the chemical effect. Mössbauer studies carried out on ((Formula presented)(Formula presented)(Formula presented)(Formula presented)(Formula presented) compounds show that there is a decrease in the hyperfine fields at various Fe sites with an increase of Al concentration. This may be due to the reduction in the Fe magnetic moment as well as the magnetic dilution, as a consequence of Al substitution. The isomer shift is found to increase with an increase in Al concentration, which is due to the reduction in the s-electron density at the nucleus, owing to the charge transfer from Al to Fe. In both series of compounds, the weighted average hyperfine fields follow a (Formula presented) behavior, which is indicative of the role of single-particle excitations in reducing the 3d sublattice magnetization with an increase in temperature. © 1997 The American Physical Society.