Effect of Core Polarization on Knight Shift and Relaxation Time in Metallic Cadmium

Abstract

The core-polarization contributions to spin density in cadmium have been obtained using the moment-perturbed (MP) procedure and leads to increases of 10 and 17% in the isotropic Knight shift ($K_s$) and the relaxation rate ${\left(T_{1}T\right)}^{-1\mathrm{}}$ at 0°K. The core-polarization effect is dominated by the $s$ part of the wave functions of the conduction electrons on the Fermi surface, and therefore produces only a small departure (1.8%) of the Korringa ratio, $R=\frac{{\left({K_s}^2{T}_{1}T\right)}_{\mathrm{expt}}}{{\left({K_s}^2{T}_{1}T\right)}_{\mathrm{ideal}}}$. Additionally, the small importance of the $p$-type core polarization indicates that the $p$ component of the conduction-electron wave function has no significant influence on the Knight shift. A comparison of our theoretical results for $K_s$ and ${\left(T_{1}T\right)}^{-1\mathrm{}}$ leads to empirical enhancement factors of ${\eta }_s=1.89\mathrm{}$ and ${\eta }_M=3.10\mathrm{}$, which are factors 1.6 and 2.4 larger than the predictions from the current-exchange enhancement theories for susceptibility. Possible sources for the origin of this discrepancy are discussed.