Rhombohedral HoNiO_3: A new half-metallic material with a high T_C, full spin-polarization and multiple Dirac-cones for advanced functional applications

摘要

A recent work by Du et al. [ACS Applied Materials & Interfaces 10 (2018): 36088-36093] showed that LaMnO_3 was a novel Dirac half metal with multiple Dirac cones. Our current work was based on their study, and the main task of our manuscript was to predict a new R3c phase material, HoNiO_3, with 100% spin-polarization and multiple Dirac-cones from first principles. The magnetic states, including FM, NM and AFM, were examined by building a 1 × 1 × 1 unit cell and two superlattice cells, i.e., 1×1×2 and 2×2×1 systems. The results showed that the FM state was the most stable magnetic state for this system. From mean-field theory (MFT), we roughly estimated the Curie temperature of the HoNiO_3 material. Although the real Curie temperature of a material is often overestimated by MFT, the high Curie temperature (T_C) value of HoNiO_3 (～902.04 K) ensured that the T_C of the material was higher than room temperature. Furthermore, the effect of spin-orbit coupling was added to examine the stabilities of the multiple Dirac cones. The results indicate that this material has long-term spin coherence, which is favourable for spin transport. The effects of the on-site Coulomb interaction U and on-site exchange constant J values on the electronic structures and magnetic moments were also examined. Moreover, the thermo-dynamic properties under different temperatures and pressures were investigated. We believe our current work will trigger further experimental and theoretical research on R3c-type Dirac half-metallic materials with multiple Dirac cones.