Electron spin resonance in heavy-fermion systems

The electron-spin-resonance (ESR) linewidth for localized moments is studied within the framework of the Kondo impurity and Kondo lattice models. An ESR signal for an impurity can only be observed if the Kondo temperature is sufficiently small. For the Kondo lattice, short-range ferromagnetic correlations between the localized spins are necessary to obtain an observable signal. These results are very similar to those derived by Abrahams and W\"olfle [Phys. Rev. B 78, 104423 (2008)] for the Anderson impurity and Anderson lattice models. It is concluded that from ESR data alone it is not possible to distinguish if the resonance is due to localized spins or conducting heavy electron spins.