Importance of anisotropic exchange interactions in honeycomb iridates. Minimal model for zigzag antiferromagnetic order in Na${}_2$IrO${}_3$

Abstract

In this work, we investigate the microscopic nature of the magnetism in honeycomb iridium-based systems by performing a systematic study of how the effective magnetic interactions in these compounds depend on various electronic microscopic parameters. We show that the minimal model describing the magnetism in A${}_2$IrO${}_3$ includes both isotropic and anisotropic Kitaev-type spin-exchange interactions between nearest and next-nearest neighbor Ir ions, and that the magnitude of the Kitaev interaction between next-nearest neighbor Ir magnetic moments is comparable with nearest neighbor interactions. We also find that, while the Heisenberg and the Kitaev interactions between nearest neighbors are correspondingly antiferro- and ferromagnetic, they both change sign for the next-nearest neighbors. Using classical Monte Carlo simulations we examine the magnetic phase diagram of the derived super-exchange model. Zigzag-type antiferromagnetic order is found to occupy a large part of the phase diagram of the model and, for ferromagnetic next-nearest neighbor Heisenberg interaction relevant for Na${}_2$IrO${}_3$, it can be stabilized even in the absence of third nearest neighbor coupling. Our results suggest that a natural physical origin of the zigzag phase experimentally observed in Na${}_2$IrO${}_3$ is due to the interplay of the Kitaev anisotropic interactions between nearest and next-nearest neighbors.

14 pages, 5 figures

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Cited by in corpus (28)

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• Hidden symmetries of the extended Kitaev-Heisenberg model: Implications for honeycomb lattice iridates A2IrO3
• Magnetization processes of zigzag states on the honeycomb lattice: Identifying spin models for $\alpha$-RuCl${}_3$ and Na${}_2$IrO${}_3$
• Honeycomb-lattice Heisenberg-Kitaev model in a magnetic field: Spin canting, metamagnetism, and vortex crystals
• Spin-orbit physics of j=1/2 Mott insulators on the triangular lattice
• Physical states and finite-size effects in Kitaev's honeycomb model: Bond disorder, spin excitations, and NMR lineshape
• Thermodynamic Evidence of Proximity to a Kitaev Spin-Liquid in Ag${}_3$LiIr${}_2$O${}_6$
• Lattice-Tuned Magnetism of Ru4+(4d4) Ions in Single-Crystals of the Layered Honeycomb Ruthenates: Li2RuO3 and Na2RuO3
• Kitaev-like honeycomb magnets: Global phase behavior and emergent effective models
• Resonant inelastic x-ray incarnation of Young's double-slit experiment
• Density-Matrix Renormalization Group Study of Extended Kitaev-Heisenberg Model
• Analysis of the optical conductivity for A2IrO3 (A = Na, Li) from first principles
• Susceptibility anisotropy and its disorder evolution in models for Kitaev materials
• Anisotropic magnetic interactions in hexagonal AB-stacked kagome lattice structures: Applications to ${\mathrm{Mn}}_3\mathrm{X}$ ($\mathrm{X}$ = $\mathrm{Ge}$, $\mathrm{Sn}$, $\mathrm{Ga}$) compounds
• Topological superconductivity in the extended Kitaev-Heisenberg model
• Spin-orbit effects in pentavalent Iridates: Models and materials
• Evidence for magnetic fractional excitations in a Kitaev quantum-spin-liquid candidate $\alpha$-RuCl${}_3$
• Non-Kitaev spin liquids in Kitaev materials
• Optical magnons with dominant bond-directional exchange interactions in a honeycomb lattice iridate $\alpha$-Li${}_2$IrO${}_3$
• Thermal conductivity of local moment models with strong spin-orbit coupling
• Topological quantum phase transition driven by anisotropic spin-orbit coupling in trinuclear organometallic coordination crystals
• On the multi-$\mathbf{q}$ characteristics of magnetic ground states of honeycomb cobalt oxides
• Bound states of fractionalized excitations in a modulated Kitaev spin liquid
• Non-Loudon-Fleury Raman scattering in spin-orbit coupled Mott insulators
• Honeycomb-lattice Gamma model in a magnetic field: hidden Néel order and spin-flop transition
• Nesting instability of gapless U(1) spin liquids with spinon Fermi pockets in two dimensions