Heavy-mass magnetic modes in pyrochlore iridates due to dominant Dzyaloshinskii-Moriya interaction

Abstract

Materials with strong spin-orbit interactions are presently a main target in the search for systems with novel magnetic properties. Magnetic anisotropies can be very large in such compounds, ranging from strongly frustrated Kitaev exchange in honeycomb iridates and the associated spin-liquid states to robust antisymmetric couplings in square-lattice Sr_2IrO_4 . Here we predict from ab initio quantum chemistry calculations that another highly unusual regime is realized in pyrochlore iridium oxides: the nearest-neighbor Heisenberg interaction can vanish whilst the antisymmetric Dzyaloshinskii- Moriya exchange reaches values as large as 5 meV, a result which challenges common notions and existing phenomenological models of magnetic superexchange. The resulting spin excitation spectra reveal a very flat magnon dispersion in the Nd- and Tb-based pyrochlore iridates, suggesting the possibility of using these modes to store magnetic information. Indeed the magnetization dynamics indicates that these modes are unable to propagate out of the excitation region.

8 pages, 4 figures

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Cited by in corpus (12)

• Magnon thermal Hall effect in kagome antiferromagnets with Dzyaloshinskii-Moriya interactions
• General method for atomistic spin-lattice dynamics with first principles accuracy
• Pressure-tuned magnetic interactions in honeycomb Kitaev materials
• Strong effect of hydrogen order on magnetic Kitaev interactions in H${}_3$LiIr${}_2$O${}_6$
• Topological magnons with nodal-line and triple-point degeneracies: Implications for thermal Hall effect in pyrochlore iridates
• First-principles Dzyaloshinskii-Moriya interaction in a non-collinear framework
• Spin-orbit coupling driven insulating state in hexagonal iridates Sr3MIrO6 (M = Sr, Na and Li)
• Large off diagonal exchange couplings and spin liquid states in ${\mathbf{C}}_3$ symmetric iridates
• Effective field theory of magnon: Dynamics in chiral magnets and Schwinger mechanism
• Superexchange interactions between spin-orbit-coupled $j\approx 1/2$ ions in oxides with face-sharing ligand octahedra
• On the connection between magnetic interactions and the spin-wave gap of the insulating phase of NaOsO${}_3$
• Metal-insulator transitions in pyrochlore oxides