Influence of Electron-Electron Interaction on the Nuclear Spin-Lattice Relaxation Rates in the Dilute Ferromagnetic AlloyPdFe

In this paper it is postulated that in exchange-enhanced alloys the $d$-hole intra-atomic exchange energy is modified at host sites with magnetic impurities as near neighbors. When this effect is statistically averaged over the alloy, the exchange enhancement that results is concentration dependent. When applied to PdFe, it is shown that one can thereby account for the rapid increase in the concentration dependence of nuclear spin-lattice relaxation rates for both Fe and Pd sites from about 3-at.% Fe on down and for the sharp peak in the concentration dependence observed at about 0.5-at.% Fe. The model is also applied to a computation of the acoustic spin-wave stiffness constant $D$. The resulting curve for $D$ vs iron concentration $c$ bends over sharply at $c$ between 1 and 3-at.% Fe, in agreement with the observed concentration dependence of $D$ in PdFe.