Korringa ratio of ferromagnetically correlated impure metals

The Korringa ratio K, obtained by taking an appropriate combination of the Knight shift and nuclear spin-lattice relaxation time, is calculated at finite temperature T in the three-dimensional electron gas model, including the electron-electron interaction U and nonmagnetic impurity scatterings. K:varies in a simple way with respect to U and T; it decreases as U is increased but increases as T is raised. However, K varies in a slightly more complicated way with respect to the impurity scatterings; as the scattering rate is increased, K increases for small U and low T,but decreases for large U or high T. This calls for a more careful analysis when one attempts to estimate the Stoner factor from K.