Oxygen-Mediated Superexchange Interactions and Their Impact on the Structural Stability, Magnetic Order, and Magnetocrystalline Anisotropy of One-Dimensional Co-Oxide Chains on Rh(553) Step-Surfaces Article uri icon

abstract

  • First-principles calculations in the framework of the generalized gradient approximation together with U on-site Coulomb corrections in the GGA %2b U approach to density functional theory (DFT) are performed to investigate the structural stability, magnetic order, and magnetocrystalline anisotropy of one-dimensional (1D) cobalt-oxide chains on Rh(553) step-surfaces. We found that the chains%27 magnetic and structural stability strongly depends on the oxygen concentration, η. It is determined that there exist competing direct ferromagnetic and indirect antiferromagnetic exchange interactions in the doped-oxygen 1D linear chains, and in general, the oxygen doping stabilizes the antiferromagnetism. For pure Co linear chains and low oxygen concentrations, in which η ≤ 0.1 monolayers (ML), the ferromagnetic solution is the ground-state magnetic configuration. For η > 0.2 ML, the antiferromagnetic arrangement stabilizes through superexchange interactions. The strong influence regarding the oxygen-doping on the Co linear chains%27 structural properties is evidenced when a small dimerization between the Co atoms at low O concentrations emerges. In contrast, dimerization in the Co chains is suppressed when the system is oxygen-freeor η > 0.2 ML. The increase of oxygen concentration strengthens the pd hybridization between Co d-states and O p-states, leading to an electronic redistribution of the majority and minority bands of the Co d-states. Such a redistribution yields to the formation of more localized bands. A significant reduction of the local magnetic moment in the Co atoms is followed. The robustness of the DFT %2b U results is also discussed to some extent. Throughout a perturbative analysis, we also investigate the oxygen dependence on the magnetocrystalline anisotropy energy (MAE) for the Co-oxide chains, which ranges from 0.4 to 1.2 meV. Interestingly, magnetization directions canted to the wires%27 direction or perpendicular to the Rh terrace are determined. Their origins are discussed in terms of the local contributions to the MAE. © 2020 ACS. All rights reserved.
  • ... more

publication date

  • 2020-01-01