Nuclear Magnetic Resonance in Dilute Tin-Based Alloys

Abstract

The magnetic resonance of the $^{119}\mathrm{Sn}$ nucleus has been observed in powdered samples of the tin-based alloys $\mathrm{Sn}\mathrm{In}$ and $\mathrm{Sn}\mathrm{Sb}$ at 4.2\ifmmode^\circ\else\textdegree\fi{}K. The observed resonance line shapes cannot be explained without invoking the eddy-current mixing of the nuclear absorption and dispersion described by Chapman, Rhodes, and Seymour. A technique for analyzing the inhomogeneously broadened tin line shape is developed which takes this effect into account explicitly. This analysis is used to determine the concentration and field dependence of the isotropic and anisotropic Knight shifts, the unmixed single-crystal linewidth, and the eddy-current-mixing ratio for both alloy series. The isotropic Knight shift is found to be approximately independent of solute concentration to 2.0-at.% solute with $|(\frac{1}{K})(\frac{\mathrm{dK}}{\mathrm{dc}})|\ensuremath{\le}0.25$. The anisotropic Knight shift is linear in solute concentration with $(\frac{1}{{K}_{A}})(\frac{d{K}_{A}}{\mathrm{dc}})$ being + 4.8 \ifmmode\pm\else\textpm\fi{} 2.8 in the $\mathrm{Sn}\mathrm{In}$ alloys and -7.7 \ifmmode\pm\else\textpm\fi{} 0.5 in the $\mathrm{Sn}\mathrm{Sb}$ alloys. The concentration and field dependence of the linewidth are in qualitative agreement with the scattering theory, and the concentration and field dependence of the eddy-current-mixing ratio are in good agreement with the theory of Chapman et al. The anomalous concentration dependence of the Knight shift in the dilute indium-rich alloys reported by Anderson, Thatcher, and Hewitt is shown to be the result of the concentration dependence of the eddy-current-mixing ratio in those alloys.