A calculation of the temperature-dependent susceptibility of Pd and dilute Pd1-xAgx and PdHx alloys

Abstract

The temperature dependence of the magnetic properties of itinerant electron systems is mainly due to the excitation of spin fluctuations. We calculate the susceptibilities of Pd, Pd1-xAgx, and PdHx (0<or=x<or=0.03) with an extension of the classical Murata-Doniach model for spin fluctuations, which treats the energy functional without a Landau expansion of the magnetization-dependent ground state energy. To obtain this energy ASW (augmented spherical wave) and KKR-CPA bandstructure calculations are performed. In agreement with experiment the KKR-CPA method yields a maximum of chi (T) for Pd, which disappears with increasing Ag concentration. In the ASW calculations, low Ag and H concentrations are simulated by the supercells Pd31Ag and Pd32H. In addition the alloy PdHx is simulated by calculations for pure Pd, with the valence electron concentration increased suitably. Calculations of the susceptibility of Pd within the framework of the Stoner theory and the spin fluctuation theory based upon the rigid-band model are presented. The role of the electron interaction in both theories is examined and the reason for the maximum of chi (T) for Pd is investigated. We find the different scaling of the temperature axis in the Stoner and spin fluctuation theories to have its origin in a different treatment of the electron interaction.