Metal-Semiconductor Transition and Antiferromagnetic State in f-Electron Systems

Abstract

The stability of antiferromagnetism and the metal-semiconductor transition are investigated in strongly correlated f-electron systems with UNiSn in mind. We introduce an effective Hamiltonian which includes the inter-atomic antiferromagnetic exchange interaction between nearest neighbor f-spins as a result of hybridization between conduction- and localized f-electrons. Based on the model, the phase diagram is investigated with regard to the magnetic and the metal-semiconductor phase transitions. We found the possible stability of the antiferromagnetic state even in the metallic phase, which was already suggested by our previous study using the perturbation expansion in the paramagnetic semiconducting state. The dependence of the Neel temperature on the energy gap is also shown to agree qualitatively with the observed behavior.