Multiband effects in the electron spin resonance of Gd3+ in the intermediate-valence compound YbAl3 and its reference compound LuAl3

Electron spin resonance (ESR) results of Gd3+ in YbAl3 and LuAl3 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 similar or equal to 14 Oe/K and b similar or equal to 9 Oe/K for Gd3+ for YbAl3 and LuAl3, respectively, are larger than those expected from the respective measured g shifts (Knight shift), and (ii) negative and positive g shifts Delta g similar or equal to-0.004 and Delta g similar or equal to+0.003 were observed for Gd3+ in YbAl3 and LuAl3, respectively. Specific heat and magnetic susceptibility measurements, in the samples studied by ESR, show that electron-electron correlations are present in both compounds.75