Electron spin resonance of Gd3+Gd3+ in the antiferromagnetic heavy fermion CeIn3CeIn3 and its reference compound LaIn3LaIn3

We report temperature dependent electron spin resonance (ESR) experiments of Gd3+Gd3+ in CeIn3CeIn3 and in its reference compound LaIn3LaIn3 taken in crushed single crystals. For LaIn3LaIn3 a single Dysonian Gd3+Gd3+ ESR line with a nearly temperature independent g~2.020(5)g~2.020(5) is observed, and its linewidth follows a Korringa-like behavior as a function of temperature. From the Korringa rate (ΔH/ΔT~16Oe/K) and gg-shift (Δg~0.027Δg~0.027) we have extracted the exchange parameter between the Gd3+Gd3+ local moments and the conduction electrons (ce) in this compound. This exchange parameter Jfs≈20meV was found to be ce wave-vector independent. For CeIn3CeIn3, the Gd3+Gd3+ ESR spectra were found to be weakly temperature dependent and present partly resolved Gd3+Gd3+ fine-structure. Interestingly, for CeIn3CeIn3, the gg-shift with respect to the gg-value of Gd3+Gd3+ in insulators is negative, in contrast to the positive gg-shift found for Gd3+Gd3+ in LaIn3LaIn3. These results suggests different electronic structure at the Gd3+Gd3+ site in the Kondo antiferromagnet host CeIn3CeIn3. Possibly, Kondo effect may cause a decrease of the ss-like conduction electron density of states at the Gd3+Gd3+ site, giving arise to an exchange interaction only between the Gd3+Gd3+ local moment and the Ce 4f electrons.