Multiband effects in the electron spin resonance ofGd3+in the intermediate-valence compoundYbAl3and its reference compoundLuAl3

Abstract

Electron spin resonance (ESR) results of ${\mathrm{Gd}}^{3+}$ in ${\mathrm{YbAl}}_{3}$ and ${\mathrm{LuAl}}_{3}$ are analyzed using a multiband ($f$-, $d$-, and $p$-type) model of correlated conduction electrons. The need for a multiband analysis of our results is based on the following observations: (i) the Korringa rates $b\ensuremath{\simeq}14\phantom{\rule{0.3em}{0ex}}\mathrm{Oe}∕\mathrm{K}$ and $b\ensuremath{\simeq}9\phantom{\rule{0.3em}{0ex}}\mathrm{Oe}∕\mathrm{K}$ for ${\mathrm{Gd}}^{3+}$ for ${\mathrm{YbAl}}_{3}$ and ${\mathrm{LuAl}}_{3}$, respectively, are larger than those expected from the respective measured $g$ shifts (Knight shift), and (ii) negative and positive $g$ shifts $\mathrm{\ensuremath{\Delta}}g\ensuremath{\simeq}\ensuremath{-}0.004$ and $\mathrm{\ensuremath{\Delta}}g\ensuremath{\simeq}+0.003$ were observed for ${\mathrm{Gd}}^{3+}$ in ${\mathrm{YbAl}}_{3}$ and ${\mathrm{LuAl}}_{3}$, respectively. Specific heat and magnetic susceptibility measurements, in the samples studied by ESR, show that electron-electron correlations are present in both compounds.