First-principles study of the electric, magnetic, and orbital structure in perovskite ScMnO₃

Perovskite ScMnO₃ has been synthesized under high temperature and high pressure. The magnetic ordering of this compound was proposed to be in the E-AFM state in previous theoretical research. Such magnetic ordering would lead the Mn³⁺ ions to be off-centered in the MnO₆ octahedra; however, this is not detected experimentally. To address this issue, we systematically investigate the magnetic, orbital, and electric structures of perovskite ScMnO₃ with first-principles calculations. It is found that its magnetic ground state is G-AFM and the magnetic ordering can explain the puzzle very well. Moreover, there is an unreported three-dimensional alternating cooperative orbital ordering in perovskite ScMnO₃. The antiferromagnetic coupling between the nearest-neighbor Mn³⁺ ions is stabilized by the strong octahedral distortions that decrease the ferromagnetic interaction between the e_g orbitals of the Mn³⁺ ions. In addition, we find that perovskite ScMnO₃ is a bipolar antiferromagnetic semiconductor in which completely spin-polarized currents with reversible spin polarization can be tuned simply by applying a gate voltage. Such controllability of the spin polarization of the current opens up new avenues for future spintronic devices. Our results not only suggest that the G-AFM phase is the ground magnetic state for perovskite ScMnO₃, but also enrich research in orbital ordering in rare-earth manganites.