Spin orientations of the spin-half Ir4+ ions in Sr3NiIrO6, Sr2IrO4, and Na2IrO3: Density functional, perturbation theory, and Madelung potential analyses

摘要: The spins of the low-spin Ir(4+) (S = 1/2, d(5)) ions at octahedral sites oxides Sr3NiIrO6, Sr2IrO4, and Na2IrO3 exhibit preferred orientations with respect to their IrO6 octahedra. We evaluated magnetic anisotropies these S 1/2 on basis density functional theory (DFT) calculations including spin-orbit coupling (SOC), probed origin by performing perturbation analyses SOC as within LS scheme. observed spin Sr3NiIrO6 Sr2IrO4 are correctly predicted DFT calculations, accounted for analysis. As orientation Na2IrO3, both experimental studies have not been unequivocal. Our analysis reveals that should nonzero components along c- a-axis directions. determined sensitive accuracy crystal structures employed, which is explained when interactions between adjacent taken into consideration. There indications implying 5d electrons less strongly localized compared those Sr2IrO4. This implication was confirmed showing Madelung potentials negative in than Most transition-metal do because induces among crystal-field split d-states, associated mixing states modifies only orbital parts states. finding cannot be mimicked a Hamiltonian this model lacks degree freedom, thereby leading spin-half syndrome. spin-orbital entanglement strong has assumed.