Effect of Pd Impurity on Charge and Spin Density in Metallic Iron Studied by Mössbauer Spectroscopy

Random iron-palladium alloys of BCC structure and containing up to 10.59 at.% of Pd have been investigated by means of 14.4keV Mössbauer spectroscopy in 57Fe at ambient temperature versus Pd concentration. It has been found that the perturbation of the iron hyperfine field caused by Pd impurity extends to the third co-ordination shell around an iron atom. Perturbations caused by single Pd atom located in the first, second and third co-ordination shell, respectively, were determined. It was found that they depend very weakly on the average Pd concentration in the range of concentrations investigated. On the other hand, similar perturbations of the isomer shift extend to greater distances from the impurity. Individual contributions due to Pd impurity in the first, second and third shell, respectively, are seen up to about 5 at.% of Pd. However they are small compared to the change of the average isomer shift due to more distant impurities. One sees the change of the average shift solely for alloys having higher concentration of Pd than 5 at.%. On the other hand, a contribution to the hyperfine field remains constant beyond the third shell at all Pd concentrations investigated. It is the same as the field in pure iron.