Compensated half-metallicity in the trigonally distorted perovskite NiCrO3

Using first-principles calculations, we investigate the electronic and magnetic properties of the trigonally distorted (R (3) over barc) perovskite-derived NiCrO3. Within the local spin-density approximation (LSDA), our calculations show that this system is an exactly compensated half-metal (CHM). The local spin moments of Cr 2.04, and antialigned Ni -1.41 and three oxygens -0.63 (in the units of mu(B)), indicate high spin S = 3/2 Cr3+ and S = 3/2 (NiO3)(3-) units. Considering reasonable values of the on-site Coulomb repulsion U on both Ni and Cr ions with LDA + U approach, this system becomes an insulator (as reported by Chamberland and Cloud) having a narrow gap in the spin-up channel, whereas the other channel has a large gap of similar to 3 eV. Although inclusion of U seemingly leads to the transition Ni2+ -> high spin S = 3/2 Ni3+, consistent with the experimentally observed effective moment, the zero net moment remains unchanged due to either reduction of oxygen local moments or enhancement of Cr local moment. Compression of volume by 10% leads to CHM even when correlation effects are included. These results suggest the possibility of a CHM state in NiCrO3 and provide another route to search for CHM, which is a property sought by many.