The Au${\mathrm{Al}}_2$-Au${\mathrm{Ga}}_2$-Au${\mathrm{In}}_2$ Problem: Knight Shifts and Relaxation Times in Their Pseudobinary Alloys

The nuclear-magnetic-resonance (NMR) and susceptibility behavior of the intermetallic compound Au${\mathrm{Ga}}_2$ differs anomalously from the isoelectric and isostructural compounds Au${\mathrm{In}}_2$ and Au${\mathrm{Al}}_2$. In an effort to test and extend the explanation offered by Jaccarino et al. and by Switendick and Narath, spin-lattice relaxation times and Knight shifts have been measured as a function of temperature and composition for the Au${\mathrm{Al}}_2$-Au${\mathrm{Ga}}_2$, Au${\mathrm{Al}}_2$-Au${\mathrm{In}}_2$, and Au${\mathrm{Ga}}_2$-Au${\mathrm{In}}_2$ pseudobinary alloy systems. At high temperature, the solute $X$ (Al, In, Ga) resonance properties are dominated by the host. Satellite resonances are observed with temperature dependences differing from the main resonance. The results are partially explainable on the basis of an average-band model and partially on a local atom model. The role of the Au $d$ bands is discussed. Metallurgical results on alloying are obtained using the NMR data.