Electronic Properties of the Grain Boundary Core in Polycrystals of Cubic Metals

Abstract

Local densities of conduction s-electrons in the grain boundary (GB) core of transition and noble metals were determined using two methods. The difference between isomer shifts of components of emission nuclear gamma resonance (NGR) spectra due to 57 Co atomic probes occupying states in the lattice sites and the grain boundary core was corrected for the change in the volume of these 57 Co atomic probes in the given states. The corrected values of the difference between isomer shifts pointed to a low density of s-electrons at the substitutional and the interstitials sites of the grain boundary core structure. The magnetic ordering temperature of nearly ferromagnetic Pd and Pt matrices was proportional to the density of conduction electrons. Different Curie temperatures in the lattice and the grain boundary core of these matrices also suggested a lower (compared to the corresponding lattice sites) density of electrons at interstitial sites of the grain boundary core structure in Pd and Pt.