Incommensurate phase of a triangular frustrated Heisenberg model studied via Schwinger-boson mean-field theory

Abstract

We study a triangular frustrated antiferromagnetic Heisenberg model with nearest-neighbor interactions J1 and third-nearest-neighbor interactions J3 by means of Schwinger-boson mean-field theory. By setting an antiferromagnetic J3 and varying J1 from positive to negative values, we disclose the low-temperature features of its interesting incommensurate phase. The gapless dispersion of quasiparticles leads to the intrinsic T2 law of specific heat. The magnetic susceptibility is linear in temperature. The local magnetization is significantly reduced by quantum fluctuations. We address possible relevance of these results to the low-temperature properties of NiGa2S 4. From a careful analysis of the incommensurate spin wavevector, the interaction parameters are estimated as J1≈-3.8755K and J 3≈14.0628K, in order to account for the experimental data. © 2009 IOP Publishing Ltd.