Evidence for Impurity Clustering and Matrix Polarization in Nickel-Palladium Alloys

Abstract

We have measured the hyperfine fields at 57Fe nuclei diffused as impurities in various nickel-palladium alloys, using the Mössbauer effect technique. In addition to the Ni–Pd matrix polarization, we find evidence of impurity clustering polarization within the same matrix. The impurity polarization effects are reduced by long term anneal of the samples. The Curie temperature of the Ni–Pd matrix exhibits a sharp rise at about 2% nickel concentration, indicating that the onset of ferromagnetism occurs at this composition in agreement with previous magnetization data. The saturation hyperfine field shows a small variation in the concentration dependence, with broad maximum centered around 45% of nickel.