High-field and multifrequency esr in the two-dimensional triangular lattice antiferromagnet niga₂s₄

We report the experimental results of electron spin resonance in high magnetic fields up to about 53 T on the quasi-two-dimensional triangular lattice antiferromagnet NiGa₂S₄. The temperature dependence of the resonance field at 584.8 GHz shows a steep change below about 30 K, indicating a development of the short-range correlation. The frequency dependence of the resonance field at the lowest temperature for H{pipe}{pipe}c is explained by one of the helical resonance modes. These experimental results suggest that the short-range order is well developed at low temperatures, and the resonance mode is described by a conventional spin wave theory.