Mixed-valence behavior of TmSe

Using the observation that the dominant interatomic coupling characteristic of mixed valence arises from the motion of f-electrons between strongly coupled Hund's rule atoms, the magnetic properties of TmSe are semi-quantitatively understood. For TmSe with Tm²⁺ concentration $\text{? 0.3}$, a transition to a state with a spontaneous net moment is predicted.