Temperature dependence of vacancy-induced electric field gradients in metals

Abstract

Electric field gradients (EFG) caused by different vacancy configurations trapped at In impurities in Cu, Zn, and Cd were measured by the PAC method. While the variation with temperature of the EFG due to monovacancies is negligibly small (or follows the temperature dependence of the EFG at substitutional lattice sites in hcp metals), a strong temperature dependence is observed for multiple vacancies, in agreement with previous experiments of Ir and Pt. The results obtained for multiple vacancy clusters can be explained quantitatively by a model based on the excitation of resonant modes in the local phonon density of states. The absence of a pronounced temperature dependence for trapped monovacancies indicates that there are either no resonant modes for these configurations or that the EFG is not sensitive to one-dimensional vibrations.