Nmr study of the electronic structure of solid and liquid metals

Abstract

NMR was used to study the effect of melting on the electronic structure of copper and aluminium. The Knight shift and spin-lattice relaxation time were measured as a function of temperature in the solid and in the liquid state. From these measurements the temperatures dependence of K(α), the reciprocal enhancement factor of the Korringa relation, is obtained. In the case of copper it is shown that the main temperature effect is indirectly through thermal expansion. It is shown that the conduction electrons density of states and spin density at the nucleus are strongly influenced by sd hybridization. Their temperature dependence is explained as due to the volume dependence of the hybridization. In aluminium, in contrast to copper, the results of K(α) as a function of temperature cannot be explained as due to volume change, but rather a direct temperature effect. The explanation is based on the strong mixing of states near the Brillouin zone. This mechanism should prevail only in polyvalent metals such as aluminium, in contrast to monovalent metals such as copper, where this effect can be neglected. The behaviour of other metals upon melting is discussed. © 1972, Walter de Gruyter. All rights reserved.