Effects of Electron-Electron Interactions on Nuclear Spin-Lattice Relaxation Rates and Knight Shifts in Alkali and Noble Metals

Abstract

Nuclear-magnetic-resonance data for the alkali and noble metals are discussed in terms of Moriya's theory of exchange-enhanced spin-lattice relaxation rates. The available evidence suggests that the relaxation-rate enhancement resulting from collective electron effects is \ensuremath{\sim}20% smaller in lithium and sodium than predicted by the theory for the case of a $\ensuremath{\delta}$-function-potential electron-electron interaction. This small disparity is attributed to a nonzero interaction range whose magnitude is estimated to be less than an atomic radius. During the course of this study, low-temperature Knight-shift and spin-lattice relaxation data have been obtained for $^{39}\mathrm{K}$, $^{85}\mathrm{Rb}$, $^{87}\mathrm{Rb}$, and $^{133}\mathrm{Cs}$ in the respective metals. The results suggest that the exchange enhancements of the conduction-electron spin susceptibilities in these metals are comparable to those in lithium and sodium. Similar conclusions apply in the case of the noble metals.