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 $b\simeq 14\mathrm{Oe}∕\mathrm{K}$ and $b\simeq 9\mathrm{Oe}∕\mathrm{K}$ 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 $\mathrm{\Delta }g\simeq -0.004$ and $\mathrm{\Delta }g\simeq +0.003$ 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.

• Received 9 August 2006

DOI:https://doi.org/10.1103/PhysRevB.75.045107