Role of oxygen vacancy in the spin-state change and magnetic ordering in SrCoO3-delta

Article

关键词: GROUND-STATE;    STOICHIOMETRIC SRCOO3;    PHASE-TRANSFORMATION;    ELECTRONIC-STRUCTURE;    AB-INITIO;    TRANSITION;    OXIDE;    POLARIZATION;    CHARGE;   

DOI  :  10.1103/PhysRevB.98.085106

来源: SCIE

【 摘 要 】

We present the first-principles investigation of the structural, electronic, and magnetic properties of SrCoO3_(delta) (delta = 0, 0.25, 0.5) to understand the multivalent nature of Co ions inSrCoO(3)_(delta) along the line of topotactic transition between perovskite SrCoO3 and brownmillerite SrCoO2.5. From the onsite Coulomb interaction U -dependent ground state of stoichiometric SrCoCO3, we show the proximity of its metallic ferromagnetic ground state to other antiferromagnetic states. The structural and magnetic properties of SrCoO3_(delta) depending on their oxygen content provide an interesting insight into the relationship between the Co-Co distances and the magnetic couplings so that the spin-state transition of Co spins can be understood by the change of pd hybridization depending on the Co-Co distances. The strong suppression of the dp sigma hybridization between Co d and O p orbitals in brownmillerite SrCoo(2.5) brings on the high-spin state of Co3+ d(6) and is responsible for the antiferromagnetically ordered insulating ground state. The increase of effective Co-Co distances driven by the presence of oxygen vacancies in SrCoO3 delta is consistent with the reduction of the effective pd hybridization between Co d and O p orbitals. We conclude that the configuration of neighboring Co spins is shown to be crucial to their local electronic structure near the metal-to-insulator transition along the line of the topotactic transition in SrCoO3_(delta). Incidentally, we also find that the I2mb symmetry of SrCoO2.5 is energetically stable and exhibits ferroelectricity via the ordering of CoO4 tetrahedra, where this polar lattice can be stabilized by the presence of a large activation barrier.

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