Ab Initio Study On Pressure-Induced Phase Transition In Lacu3fe4o12

The electronic structure and magnetic ordering in LaCu3Fe4O12 are theoretically studied by means of ab initio calculations. To clarify the microscopic mechanism for the experimentally observed phase transitions induced both by pressure and temperature, the cell-volume dependence of total energy is calculated. It is found that the electronic structure changes from insulating to metallic as the Cu valence shifts from nonmagnetic Cu3+ (S = 0) to spin-polarized Cu2+ (S = 1/2) at the transition pressure (or temperature). The electronic state of Cu is important since it is coupled with the metallicity of the electronic structure via the inter-site charge transfer. The pressure-induced phase transition in LaCu3Fe4O12 is explained by the difference in the bulk modulus between the insulating ground state and the metallic high-pressure phase. The mechanism for the temperature-induced phase transition is also proposed in terms of the magnetic configurational entropy of the magnetic moment of Cu spins.