Pressure-induced spin-state and insulator-metal transitions in Sr₃Fe₂O₅ from first principles

¹ Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences Hefei 230031, PRC
² Laboratory for Computational Physical Sciences (MOE), State Key Laboratory of Surface Physics, and Department of Physics, Fudan University - Shanghai 200433, PRC
³ Department of Physics, University of Science and Technology of China - Hefei, 230026, PRC
⁴ Department of Physics and Institute of Theoretical Physics, The Chinese University of Hong Kong Shatin, Hong Kong PRC

^(a) wuh@fudan.edu.cn (corresponding author)
^(b) zzeng@theory.issp.ac.cn (corresponding author)

Received: 21 March 2013
Accepted: 5 June 2013

Abstract

Using hybrid functional calculations, we find that under the experimental pressure of 36.7 GPa, layered Sr₃Fe₂O₅ undergoes a spin-state transition (SST) from high spin to intermediate spin. This transition is triggered by an electron depletion of the highest crystal-field level x² − y². On the other hand, a reduced inter-layer distance lifts up the antibonding 3z² − r² state, and thus its electron occupation is partially shifted to the otherwise unoccupied x² − y² conduction band. This gives rise to an insulator-metal transition (IMT). We note that the IMT is closely related to the SST, but they somewhat have a different origin.