Isoelectronically substituted heavy-fermion compoundsCeCu6−xAux, studied by local probe and electronic band structure calculation

Abstract

For $\mathrm{Ce}{\mathrm{Cu}}_{6\ensuremath{-}x}{\mathrm{Au}}_{x}$ $(x=0,0.1,1)$, we measured the temperature dependence of $^{63,65}\mathrm{Cu}$ nuclear magnetic resonance spectra of oriented single-crystal powder at $7\phantom{\rule{0.3em}{0ex}}\mathrm{T}$ in the $5--100\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ range. ${\mathrm{Ce}}^{3+}$ crystal field and molecular field parameters are derived from single-crystal magnetic susceptibility data. Calculated electric field gradients are used to correctly assign nuclear quadrupole resonance frequencies to lattice sites $(n)$. Bare Knight shifts and transferred hyperfine interaction coupling constants $\ensuremath{\alpha}(n)$ as well as electric field gradient information are extracted for the various Cu sites $(n)$. Ab initio self-consistent energy-band calculations explain the electric field gradients and the alternation of the sign of $\ensuremath{\alpha}(n)$. The anisotropy of the hyperfine coupling parameter $\ensuremath{\alpha}$ is proved for the $a\text{\ensuremath{-}}c$ plane for the Cu(5) site.