First principles simulation of temperature dependent electronic transition of FM-AFM phase BFO

Abstract

Understanding how temperature affects the electronic transitions of BFO is important for design of BiFeO3 (BFO)-based temperature-sensitive device. Hitherto, however, there have been only very limited reports of the quantitative simulation. Here, we used density functional theory (DFT) and two-dimensional correlation analysis (2D-CA) techniques to calculate the systematic variations in electronic transitions of BFO crystal, over a range of temperature (50~1500 K). The results suggest that the heat accumulation accelerates the O-2p4 orbital splitting, inducing the Fe3+-3d5→Fe2+-3d5d0 charge disproportionation. The origin is observed as the temperature-dependent electron transfer process changes from threefold degeneracy to twofold degeneracy. Additionally, the crystallographic orientation (111) can be used to control the 2p-hole-induced electronic transition as O→unoccupied Fe3+-3d5, in comparison to the O→Bi-6p3+Fe3+-3d5d0 on the orientations (001) and (101). This study offers new perspective on the improvement of BFO-based temperature-sensitive device.