NUCLEAR-RESONANCE OF YTTERBIUM LOCAL MOMENTS IN GOLD

We have observed the Yb173 nuclear resonance in dilute AuYb alloys using a phase-coherent spin-echo spectrometer in the frequency range 450-530 MHz, with external fields of 67-119 kOe and temperatures of 1-2 K. At these field strengths and temperatures, the electronic moment is strongly polarized and the local-moment relaxation regime ωeT2e1 applies. The resonance has been studied in both powders and single crystals. The field dependence of the resonance frequencies can be fit with a crystal-field splitting Δ(Γ8-Γ7)=83.7(±2.5) K and a hyperfine constant Ah=-241.5(±1.0) MHz. These values agree well with those obtained in electron-spin-resonance, Mössbauer, and magnetic-susceptibility experiments. The transverse nuclear relaxation time varies as T2T-1 and T2H02. The measured rates agree with predictions for the 1/2 -1/2 nuclear transition based on a model involving local-moment fluctuations within the Γ7 ground-state doublet using a conduction-electron exchange constant I2ρ2=0.018 derived from the reported thermal broadening of the ytterbium ESR. The absence of significant contributions to the observed high-field relaxation rates from Γ7-Γ8 fluctuations provides strong evidence that the local-moment-conduction-electron interaction in AuYb is principally of an anisotropic form. © 1979 The American Physical Society.