Pressure driven spin crossover and isostructural phase transition in LaFeO3

Abstract

We have studied the behavior of LaFeO3 under pressure (P) using density functional theory (DFT) and atomistic simulations. Ground state structural properties of LaFeO3 are correctly described by atomistic simulations. The effect of high pressure shows that there is an isotropic compression up to 100 GPa. However, DFT calculations show that within pressure range 0 < P < 32.4 GPa, LaFeO3 retains its ground state electronic structure. On the other hand, at P ∼32.4 GPa high to low spin magnetic phase transition is observed, which is accompanied by 6.9% volume collapse of LaFeO3 unit cell, while retaining the ground state orthorhombic crystal structure, i.e., isostructural phase transition. Furthermore, the band gap is closed leading insulator to metal transition. This differing behavior observed by the two techniques can be attributed to the omission of magnetic effects in static simulations. The simultaneous magnetic, electrical, and structural (volume collapse) phase transitions of LaFeO3 under compression as revealed by DFT calculations corroborate experimental findings. From these results, we can elaborate the mechanism of phase transition in LaFeO3: increasing crystal field induces a high spin to low spin transition, which in turn drives the electrical transitions and volume collapse.