Why could electron spin resonance be observed in a heavy fermion Kondo lattice?
Theoretical Physics Departement, Kazan State University, 420008 Kazan, Russia
2 Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany
Corresponding author: a email@example.com
Revised: 15 October 2009
Published online: 10 November 2009
We develop a theoretical basis for understanding the spin relaxation processes in Kondo lattice systems with heavy fermions as experimentally observed by electron spin resonance (ESR). The Kondo effect leads to a common energy scale that regulates a logarithmic divergence of different spin kinetic coefficients and supports a collective spin motion of the Kondo ions with conduction electrons. We find that the relaxation rate of a collective spin mode is greatly reduced due to a mutual cancellation of all the divergent contributions even in the case of the strongly anisotropic Kondo interaction. The contribution to the ESR linewidth caused by the local magnetic field distribution is subject to motional narrowing supported by ferromagnetic correlations. The developed theoretical model successfully explains the ESR data of YbRh2Si2 in terms of their dependence on temperature and magnetic field.
PACS: 76.30.Kg – Rare-earth ions and impurities / 71.27.+a – Strongly correlated electron systems; heavy fermions / 75.40.Gb – Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.)
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2009