Pressure-Induced Phase Diagram and Electronic Structure Evolves during the Insulator–Metal Transition of Bulk BiFeO₃

Abstract

BiFeO 3 is the most widely known multiferroic at room temperature, possessing both ferroelectricity and antiferromagnetism. It has high Curie temperature and Neél temperature, i.e., 1103 and 643 K, respectively. Despite these unique properties, the pressure-induced phase diagram of bulk BiFeO 3 has remained controversial. Based on the ab initio evolutionary algorithm, we systematically searched for the potential stable structures of bulk BiFeO 3 at 0−50 GPa. It is identified that there are five pressure-induced phase transition sequences R3c−G−AFM → (5GPa) C2/m−G−AFM → (15GPa) Pnma−G−AFM → (24GPa) Pnma− FM → (35GPa) Imma−FM → (45GPa) Cmcm−FM, which provided a comprehensive pressure-induced phase diagram.As the pressure increases, we discovered an interesting phenomenon: a pressure-induced magnetic sequence transition, i.e., BiFeO 3 transitions from an antiferromagnetic to a ferromagnetic sequence. Concurrently, the electronic structure evolves during the insulator−metal transition, influenced not only by the pressure but also by the phase transition. Our research has elucidated the long-standing question of the phase transition sequence of the BiFeO 3 system under pressure and provided theoretical support for the insulator− metal transition.