Simultaneous metal–half-metal and spin transition in SrCoO₃ under compression

Han Hsu^1*, Sheng-Chieh Huang¹

¹Department of Physics, National Central University, Taoyuan City, Taiwan

* Presenter:Han Hsu, email:hanhsuphys@gmail.com

In experiments, strontium cobaltite (SrCoO₃) has been confirmed to be a ferromagnetic metal (Curie temperature T_C ≈ 305K) at ambient conditions and remains in cubic perovskite structure up to ~60 GPa. Using local density approximation + self-consistent Hubbard U (LDA+U_sc) calculations, we show that ferromagnetic metallic SrCoO₃ at low pressure is in an intermediate-spin (IS) state with d₆L character: nearly trivalent (Co³⁺) instead of tetravalent cobalt (Co⁴⁺) accompanied by spin-down O-2p electron holes (ligand holes L). Our calculations further predict that upon compression (≧ 7 GPa), SrCoO₃ undergoes a transition to a low-spin (LS) ferromagnetic half-metal with an energy gap opened in the spin-up channel. Compared to the metallic IS state, the half-metallic LS state exhibits even more prominent d₆L character, including nearly nonmagnetic Co³⁺ and exceptionally large oxygen magnetic moments, which contribute most of the magnetization. By analyzing x-ray diffraction data of compressed single-crystal SrCoO₃, we point out an anomalous volume reduction (~1%) that has not been reported before. This previously unnoticed volume anomaly is in great agreement with our predictive calculations, providing quantitative evidence for the simultaneous metal–half-metal and spin transition in SrCoO₃.

Keywords: Ferromagnets, Half-metals, Perovskite, High-pressure, First-principles