NUCLEAR SPIN-LATTICE RELAXATION IN LIQUID Li-Na, Li-Mg AND Li-Pb ALLOYS

Abstract
The nuclear spin-lattice relaxation rate T^-1₁ of ⁸Li in liquid Li-Na, Li-Mg and Li-Pb alloys has been measured by means of the asymmetric β-decay radiation of polarized ⁸Li (T_1/2 = 0.8s) nuclei as a function of temperature T and solute concentration c. T^-1₁ is dominated by magnetic hyperfine interaction with conduction electrons. The reduced rate (T₁T)^-1 depends slightly on T in a way which, for Li-Na and Li-Mg, is similar to that reported for the electrical resistivity. The T dependence of the liquid structure is assumed to be the main reason for both these findings. (T₁T)^-1/2 varies about linearly with c in Li-Na and Li-Mg and obeys the Korringa relation (T₁T)^-1/2 = const.K in Li-Na, where the Knight shift K is known, over the entire c-range. In Li-Pb, however, (T₁T)^-1/2 has a marked minimum near c= 20 at% Pb which can be ascribed to the compound forming tendency of Li and Pb in the melt. Comparison with recent Knight shift measurements shows that the measured rate is significantly enhanced over the Korringa rate around c =20 at%. The result fits into the scheme proposed by Warren which relates the enhancement to the electrical conductivity in the strong scattering regime.