Materials Science and Nanotechnology

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2nd International Conference on MAGNETISM AND MAGNETIC MATERIALS
September 24- 26 , 2018 | Budapest , Hungary

Alexander Yaresko

Max Planck Institute for Solid State Research, Germany

Posters & Accepted Abstracts : Mater Sci Nanotechnol


Because of strong spin-orbit coupling within the Iridium 5d shell magnetic interaction in Ir4+ oxides cannot be described by an isotropic Heisenberg-like model and anisotropic exchange interactions become important. In α-Na2IrO3 and α-Li2IrO3, in which edge sharing IrO octahedra form a honeycomb lattice, magnetic interaction was suggested to be bond-dependent and to be described by the Kitaev model. Recently, another complex Ir oxide β-Li2IrO3 has been synthesized which is expected to be close to forming a Kitaev spin liquid. Ir ions in this compound form a “hyper-honeycomb” lattice, a three-dimensional analogue of the honeycomb lattice of α-Na2IrO3. In Sr2IrO4, Sr3Ir2O7 and in R2Ir2O7 compounds, where R is a rare-earth ion, with the pyrochlore structure, on the other hand, the dominant anisotropic exchange is the anti-symmetric Dzyaloshinskii–Moriya interaction. We present results of LSDA+U band structure calculations for Na2IrO3, Sr2IrO4, and some R2Ir2O7 iridates. The strength of the Coulomb repulsion U is adjusted by comparing the calculated optical conductivity to experimental optical spectra. Then, magnetic interactions in these compounds are estimated by mapping the total energy calculated for various non-collinear magnetic configurations constrained by magnetic symmetry onto an effective model which includes isotropic Heisenberg-like as well as bond-dependent anisotropic magnetic interactions. It is shown that the variation of the total energy cannot be described by the isotropic Heisenberg-like model and anisotropic terms may be as strong as the isotropic ones.



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