Myung-Chul Jung, Young-Joon Song, K. -W. Lee, W. E. Pickett
The orthorhombic perovskite NaOsO3 undergoes a continuous metal-insulator transition (MIT), accompanied by antiferromagnetic order at T_N=410 K, suggested to be an example of the Slater (itinerant) MIT. We have investigated this system using ab initio methods to probe the origin and nature of magnetic ordering and the MIT. The rotation and tilting of OsO6 octahedra in the GdFeO3 structure result in moderate narrowing the band width of the $t_{2g}$ manifold, but sufficient to induce antiferromagnetic (AFM) order. Within the local density spin approximation (LSDA), the system magnetically orders but remains metallic with a deep pseudogap. Considering correlation effects by including on-site Coulomb repulsion U, at U_{c} ~ 1.5 - 2 eV a MIT occurs only in the AFM state. Effect of spin-orbit coupling (SOC) are small in this half-filled $t_{2g}^{3}$ shell, although it leads to an increase in the critical value U_{c} necessary to open a gap. Our results indicate that this MIT is driven by the magnetic order, induced by a combination of structurally-induced band narrowing and moderate Coulomb repulsion. Strong p-d hybridization, and not SOC, substantially reduces the magnitude of the net moment to ~1 $\mu_B$, one third of the formal moment and a value that is consistent with the observed moment.
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http://arxiv.org/abs/1210.1286
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