Ground state properties of perovskite and post-perovskite CaRuO 3: Ferromagnetism reduction

Abstract

Aiming at the disputed ground state properties of perovskite (Pv) CaRuO 3, we have investigated the variations of electronic structures and magnetism between Pv and post-perovskite (PPv) phases of CaRuO 3, based on the generalized gradient approximation (GGA) plus on-site Coulomb interaction U and spin-orbital coupling (SOC) effect correction, namely GGA + U + SOC method. Both Pv and PPv phases have Mott-Hubbard insulating characteristics. Under Pnma symmetry, the 4 d electrons have the stronger SOC effect and the weaker electronic correlation. Under Cmcm symmetry, however, the situation is just reversed. The G-type antiferromagnetic (AFM) superexchange interaction of Ru–Ru is perfected in Pv phase, antiferromagnetically mediated by O atoms. PPv phase exhibits the AFM ground state along c direction, but the FM–AFM fluctuation exists in a– b plane of PPv phase. The strong magnetic anisotropy and big exchange constants are the inexistent evidences of spin-glass behavior in Pv and PPv phases. Ru 4+ is in low-spin state, S ∼ 1. Pv–PPv phase transition changed the electronic and magnetic structures, but the magnetism is not sensitive to pressure in each phase. The suppression of ferromagnetism in Pv and PPv phases arises from the AFM interaction induced by the SOC effect and the FM–AFM fluctuation, respectively.