Spin gap formation in SmB6

Abstract The precise measurements of magnetic properties have been carried out on single crystals of SmB 6 for temperatures down to 4.2 K. It is shown that the non-monotonic temperature dependence of magnetic susceptibility χ ( T ) of SmB 6 at T >50 K can be well approximated by an activation type contribution χ a ( T )∼1/ T  exp(− E a / k B T ) with E a / k B ∼65 K. This behaviour can be attributed to a spin gap formation with thermally induced magnetic moments characterized by the value of μ eff ∼1.6μ B . A correlation between the “intra-gap contribution” Δχ ( T )= χ ( T )− χ a ( T ) observed below 50 K and temperature-dependent excitations appearing in inelastic neutron and Raman scattering spectra of SmB 6 at T