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Commensurate and incommensurate magnetic order in spin-1 chains stacked on the triangular lattice in Li2NiW2 O8
K. Ranjith M., R. Nath, D. Kasinathan, M. Skoulatos, L. Keller, Y. Skourski, M. Baenitz, A. Tsirlin A.
Published in
2016
Volume: 94

Issue: 1
Abstract
We report the thermodynamic properties, magnetic ground state and microscopic magnetic model of the spin-1 frustrated antiferromagnet Li2NiW2O8, showing successive transitions at TN1≃18 K and TN2≃12.5 K in zero field. Nuclear magnetic resonance and neutron diffraction reveal collinear and commensurate magnetic order with the propagation vector k=(12,0,12) below TN2. The ordered moment of 1.8$\mu$B at 1.5 K is directed along [0.89(9),-0.10(5),-0.49(6)] and matches the magnetic easy axis of spin-1Ni2+ ions, which is determined by the scissor-like distortion of the NiO6 octahedra. Incommensurate magnetic order, presumably of spin-density-wave type, is observed in the region between TN2 and TN1. Density-functional band-structure calculations put forward a three-dimensional spin lattice with spin-1 chains running along the [011] direction and stacked on a spatially anisotropic triangular lattice in the ab plane. We show that the collinear magnetic order in Li2NiW2O8 is incompatible with the triangular lattice geometry and thus driven by a pronounced easy-axis single-ion anisotropy of Ni2+.