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arXiv · 0803.0718

Short-range magnetic ordering process for the triangular lattice compound NiGa2S4: a positive muon spin rotation and relaxation study

A. Yaouanc·P. Dalmas de Reotier·Y. Chapuis·C. Marin·G. Lapertot·A. Cervellino·A. Amato
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Abstract

We report a study of the triangular lattice Heisenberg magnet NiGa2S4 by the positive muon spin rotation and relaxation technique. We unravel three temperature regimes: (i) below T_c = 9.2(2) K a spontaneous static magnetic field at the muon site is observed and the spin dynamics is appreciable: the time scale of the modes we probe is ~ 7 ns; (ii) an unconventional stretched exponential relaxation function is found for T_c < T < T_{cross} where T_{cross} = 12.6 K, which is a signature of a multichannel relaxation for this temperature range; (iii) above T_{cross}, the relaxation is exponential as expected for a conventional compound. The transition at T_c is of the continuous type. It occurs at a temperature slightly smaller than the temperature at which the specific heat displays a maximum at low temperature. This is reminiscent of the behavior expected for the Berezinskii-Kosterlitz-Thouless transition. We argue that these results reflect the presence of topological defects above T_c.

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A. Yaouanc, P. Dalmas de Reotier, Y. Chapuis, C. Marin, G. Lapertot, A. Cervellino, A. Amato. 2008-03-06. Short-range magnetic ordering process for the triangular lattice compound NiGa2S4: a positive muon spin rotation and relaxation study. https://doi.org/10.1103/physrevb.77.092403

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