Temperature evolution of Pr-ion magnetic response in PrB6

Inelastic neutron scattering study of PrB6 in paramagnetic and antiferromagnetic phases has been performed. It has been established experimentally that Gamma5 triplet is the ground state for PrB6 in a paramagnetic phase. A transition to magnetically ordered phase at T=7K results in a splitting of Gamma5 triplet. The second transition at T=4K gives an additional contribution to the ground state splitting. The origin of this contribution can be related to the increase of a mean magnetic field or a structural distortion with a reduction of a local symmetry due to phase transition.