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Incommensurate counterrotating magnetic order stabilized by Kitaev interactions in the layered honeycomb α − Li 2 IrO 3

DOI: 10.1103/PhysRevB.93.195158 DOI Help

Authors: S. C. Williams , R. d. Johnson (University of Oxford, ISIS) , F. Freund (Augsburg University) , Sungkyun Choi (University of Oxford) , A. Jesche (Augsburg University) , I. Kimchi (Massachusetts Institute of Technology) , S. Manni (Augsburg University) , Alessandro Bombardi (Diamond Light Source) , Pascal Manuel (ISIS) , P. Gegenwart (Augsburg University) , Radu Coldea (University of Oxford)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Physical Review B , VOL 93

State: Published (Approved)
Published: May 2016
Diamond Proposal Number(s): 12028

Abstract: The layered honeycomb magnet α-Li2IrO3 has been theoretically proposed as a candidate to display novel magnetic behaviour associated with Kitaev interactions between spin-orbit entangled jeff=1/2 magnetic moments on a honeycomb lattice. Here we report single crystal magnetic resonant x-ray diffraction combined with powder magnetic neutron diffraction to reveal an incommensurate magnetic order in the honeycomb layers with Ir magnetic moments counter-rotating on nearest-neighbour sites. This type of magnetic structure has not been reported experimentally before in honeycomb magnets and cannot be explained by a spin Hamiltonian with dominant isotropic (Heisenberg) couplings. The magnetic structure shares many key features with the magnetic order in the structural polytypes β and γ-Li2IrO3, understood theoretically to be stabilized by dominant Kitaev interactions between Ir moments located on the vertices of three-dimensional hyperhoneycomb and stripyhoneycomb lattices, respectively. Based on this analogy and a theoretical soft-spin analysis of magnetic ground states for candidate spin Hamiltonians, we propose that Kitaev interactions also dominate in α-Li2IrO3, indicative of universal Kitaev physics across all three members of the harmonic honeycomb family of Li2IrO3 polytypes.

Subject Areas: Physics

Instruments: I16-Materials and Magnetism