The spin nematic state in triangular antiferromagnets

Motivated by the recently discovered triangular magnet NiGa2S4, we investigated a spin antiferronematic phase in the spin- 1 bilinear - biquadratic model. We obtained the energy dispersion of elementary excitations by bosonizing spin operators, and the dynamic and static spin correlations are calculated. Low energy properties of NiGa2S4 are consistently explained using the scenario of nematic order, including the algebraic temperature dependence of the specific heat C( T) similar to T-2 and a finite value of the magnetic susceptibility at zero temperature. We also calculated the rate of relaxation of the nuclear magnetic resonance, and found T-1(-1) alpha T-3, a scaling different from that in the magnetically ordered phase. Some comments are also given on how to identify antiferronematic orders experimentally.