ORBITAL CONTRIBUTION TO THE MAGNETIC HYPERFINE FIELD OF ISOLATED Ni IMPURITIES IN Pd

The temperature, magnetic field and concentration dependence of the magnetic hyperfine field of Ni impurities in Pd and PtPd alloys were determined by measuring the Larmor frequency shift of isomeric states in the 63Ni isotope using the PAD method. The recoil implanted Ni nuclei, products of heavy ion reactions, were distributed in practically infinite dilution in the hosts. The magnetic hyperfine field for Ni in Pd was compared with its susceptibility contribution obtained from extrapolated susceptibility measurements in dilute NiPd alloys. Within a simple molecular field model the different contributions to the hyperfine field could be estimated. The negative core polarization field of the impurity spin moment is compensated by a transferred hyperfine field correlated with the host polarization in the neighbourhood of the impurity. The observed positive hyperfine field is due to an orbital moment of 0.3 µB at the impurity site. The values obtained for the different contributions agree with extrapolated results from KKR-CPA calculations for concentrated NiPd alloys