EPR ofGd3+Impurities in a Host with Interconfiguration Fluctuations

The EPR of ${\mathrm{Gd}}^{3+}$ impurities in the interconfiguration-fluctuation (ICF) host Ce${\mathrm{Pd}}_3$ is reported. The observed linewidth is consistent with an intrinsic relaxation rate proportional to $T$, where the proportionality constant is 3 times smaller than in the isostructural non-ICF host Y${\mathrm{Pd}}_3$. Although contrary to what is suggested by simple fluctuation concepts, such an effect of ICF on the EPR linewidth is actually to be expected theoretically.