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

Perovskite ScMnO 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 Mn ions to be off-centered in the MnO octahedra; however, this is not detected experimentally. To address this issue, we systematically investigate the magnetic, orbital, and electric structures of perovskite ScMnO 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 ScMnO. The antiferromagnetic coupling between the nearest-neighbor Mn ions is stabilized by the strong octahedral distortions that decrease the ferromagnetic interaction between the e orbitals of the Mn ions. In addition, we find that perovskite ScMnO 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 ScMnO, but also enrich research in orbital ordering in rare-earth manganites.