Silver Nuclear Magnetic Resonance in Silver-Transition-Metal Solid Solutions

The nuclear magnetic resonance of ${\mathrm{Ag}}^{109}$ has been studied in binary silver solid solutions containing Pd, Pt, Ni, and Mn. Knight shifts and cw absorption linewidths are reported as a function of solute concentration $c$, temperature $T$, applied field $H$, and annealing time. The silver absorption line is broadened rapidly by the addition of Mn and has an $H$, $T$, and $c$ dependence given by $\frac{\Delta H_{\mathrm{imp}}}{H}=[0.8+\frac{120}{\mathrm{}(T+55\mathrm{})\mathrm{}}]c\times {10}^{-3\mathrm{}}$ ($T$ in °K). The presence of magnetic moments on the Mn ions is inferred, with, however, some interaction between moments. Only in Ag: Mn is the linewidth appreciably temperature dependent. The width is believed to be due to direct magnetic dipole coupling between Ag nuclei and Mn ions and Ruderman-Kittel-Kasuya-Yosida spin-density oscillations. Representation of $〈S_z〉$ for Mn ions by a modified Brillouin function leads to qualitative agreement with experiment. A sharp narrowing of the linewidth following annealing is believed to be due to loss of solute by internal oxidation. The line shape becomes more Lorentzian as Mn is added to Ag. For Ag: Ni and Ag: Pt, the line broadening is only about one-third of that observed in Ag: Mn. The change in the ${\mathrm{Ag}}^{109}$ Knight shift $K$ upon alloying with Ni, Pt, or Mn is small, $\frac{\Delta K}{K}\lesssim -1\%$. The shift in Ag: Pd is negative and nonlinear in concentration with $\frac{\Delta K}{K}=-3\%$ at 10% Pd and -10.5% at 20% Pd, in agreement with pulse measurements of Narath. The line broadening in Ag: Pd is proportional to $c$ up to $c=10\%$ and varies as $\sqrt{c}$ for higher concentrations. The broadening is discussed in terms of simple band theory and virtual bound states. Line broadening produced by equiatomic percentage of $d$-shell impurities is compared. Finally, a comparison with other systems, particularly Cu: Mn, is made.