Magnetic excitation spectrum of mixed-valence SmB6 studied by neutron scattering on a single crystal

The paramagnetic response of mixed-valence samarium hexaboride has been studied by inelastic neutron scattering using a low-absorption double-isotope single crystal of 154Sm11B6. Measurements were performed for energy transfers 0≤h x ω ≤ 50 meV at temperatures ranging from 2 to 100 K. Two main contributions were observed in the spectra: a broad intermultiplet transition of single-ion type at h x ω ≅ 36 meV, and a narrow low-energy excitation centred at h x ω ≅ 14 meV, which is strongly anisotropic and temperature dependent and exhibits a weak but visible dispersion. The latter excitation appears to be an inherent feature of the mixed-valence state due to f-electron hybridization effects, which denotes the formation of a local bound state around the Sm sites. (author)