Renormalization of antiferromagnetic spin waves in heavy fermion compounds with TNe´el≈TKondo

Recent inelastic neutron scattering experiments in CeIn3CeIn3 and CePd2Si2CePd2Si2 single crystals measured spin wave excitations at low temperatures. These two heavy fermion compounds exhibit antiferromagnetic (AF) long-range order, but a strong competition between the Ruderman–Kittel–Kasuya–Yosida (RKKY) interaction and Kondo effect is evidenced by their nearly equal Néel and Kondo temperatures. Our aim is to show how magnons such as measured in the AF phase of these Ce compounds, can be described within a microscopic Heisenberg–Kondo model introduced by Iglesias, Lacroix and Coqblin, previously applied to study the non-magnetic phase. The model includes the Ce-4f local moments, assumed in AF order, and Kondo-coupled with the electrons in the conduction band, where we also allow for Hubbard correlation possibly inducing an AF state. We consider competing RKKY (Heisenberg-like JHJH) and Kondo (JKJK) AF couplings. Carrying on a series of unitary transformations, we perturbatively derive a second-order effective Hamiltonian which, averaged onto the AF electron ground state, describes the AF spin wave excitations, renormalized by their interaction with correlated itinerant electrons. We numerically study how the different parameters of the model influence the renormalization of the magnons, yielding useful information for the analysis of inelastic neutron scattering (INS) experiments in AF heavy fermion compounds. We also compare our results with the available experimental data, finding good agreement with the spin wave measurements in cubic CeIn3CeIn3.