First evidence for a Sm$^{3+}$-type contribution to the magnetic form factor in the quasielastic spectral response of intermediate valence SmB$_6$

The momentum transfer dependence of the magnetic form factor associated with the quasielastic spectral component in the dynamic magnetic response of intermediate valence SmB$_{6}$ has been measured using inelastic neutron scattering on a double-isotope ($^{154}$Sm, $^{11}$B) single crystal. The experimental dependence differs qualitatively from those obtained earlier for the inelastic signals, as well as from the field-induced magnetic form factor of SmB$_6$ obtained by polarized neutron diffraction. This observation is interpreted by specifically considering the Curie-type contributions to the dynamic susceptibility, which arise from the mixing of $4f^5$ and $4f^6$ $J$-multiplets into the intermediate valence state wave function.