Anomalous ferromagnetism and magneto-optical Kerr effect in semiconducting double perovskite Ba2NiOsO6 and its (111) (Ba2NiOsO6)/(BaTiO3)10 superlattice
Journal
Physical Review B
Journal Volume
100
Journal Issue
5
Date Issued
2019
Author(s)
Lu H.-S., Guo G.-Y.
Abstract
We carry out a first-principles investigation on magnetism, electronic structure, magneto-optical effects, and topological property of newly grown cubic double perovskite Ba2NiOsO6 and its (111) (Ba2NiOsO6)/(BaTiO3)10 superlattice, based on the density functional theory with the generalized gradient approximation (GGA) plus onsite Couloumb interactions. Interestingly, we find that both structures are rare ferromagnetic (FM) semiconductors with estimated Curie temperatures of ?150 and 70 K, respectively. The calculated near-neighbor exchange coupling parameters reveal that the ferromagnetism is driven by exotic FM coupling between Ni and Os atoms, which is due to the FM superexchange interaction caused by the abnormally strong hybridization between the half-filled Ni eg and unoccupied Os eg orbitals. The strong spin-orbit coupling (SOC) on the Os atom is found to not only open the semiconducting gap but also produce a large antiparallel orbital magnetic moment on the Os atom, thus reducing the total magnetization from 4.0μB/f.u., expected from the Ni2+3d8 (t2g6eg2; S=1) and Os6+5d2(t2g2eg0; S=1) ions. Remarkably, we also find that because of the enhanced exchange interaction on the Os atoms caused by the Ni 3d-Os 5d hybridization and the strong SOC of the Os atoms, the magneto-optical (MO) effects are large in these two structures. For example, the Kerr and Faraday rotations in bulk Ba2NiOsO6 can be reach 6 and 250deg/μm, respectively, which are larger than that of best-known MO materials. These interesting findings thus suggest that because of their FM semiconductivity and excellent MO properties, both structures would be promising materials for not only semiconductor-based spintronics but also magneto-optical devices. Finally, our calculated anomalous Hall conductivity shows that the band gap just below the Fermi level in the superlattice is topologically nontrivial with the gap Chern number of 2. This indicates that the (111) Ba2NiOsO6 and related 5d double-perovskite monolayers may provide an interesting material platform for exploring magnetic topological phases and phase transitions. ? 2019 American Physical Society.
Subjects
Atoms; Barium titanate; Density functional theory; Electronic structure; Energy gap; Ferromagnetism; Frequency modulation; Magnetic moments; Nickel; Nickel compounds; Perovskite; Semiconductor devices; Topology; Anomalous ferromagnetisms; First-principles investigations; Generalized gradient approximations; Magneto-optical Kerr effects; Orbital magnetic moment; Spin-orbit couplings; Superexchange interaction; Topological properties; Optical Kerr effect
Type
journal article