Microscopic and macroscopic electronic properties of the AuCu3-type alloys: The LaSn3-LaIn3 pseudobinary alloy system

Abstract

The bulk properties of the LaSn3xIn3(1-x) and similar alloy systems display a dramatic, somewhat oscillatory, dependence on the valence-electron concentration. For the LaSn3xIn3(1-x) alloy system we have studied the dependence on x of the magnetic susceptibility χ and the local electronic behavior at the La and Sn-In sites using the La139 and Sn119 nuclear-magnetic-resonance Knight shifts K and spin-lattice relaxation times T1. These results are compared with those for the superconducting transition temperature Tc, the electronic-specific-heat coefficient γ, and the Debye temperature ΘD. Using McMillan's strong-coupling model we have calculated from γ and TcΘD, the electron-phonon coupling parameter λ, the bare density of states N(0), and the electron-phonon interaction strength V. For the NMR measurements, the Sn NMR properties follow the behavior of the bulk density of states at the Fermi energy, N(0), considerably better than do the La NMR properties suggesting that the local electronic properties of the Sn-In sites play the dominant role in determining Tc. Analysis of the La NMR and χ behavior with x indicates the paramagnetic susceptibility of these alloys arises from the La d band with the La d-orbital contribution accounting for most of the large susceptibility for x near LaSn3 and LaIn3. © 1973 The American Physical Society.