Possible ferro-spin nematic order in NiGa2S4

We explore the possibility that the spin-1 triangular lattice magnet NiGa2S4 may have a ferronematic ground state with no frozen magnetic moment but a uniform quadrupole moment. Such a state may be stabilized by biquadratic spin interactions. We describe the physical properties of this state and suggest experiments to help verify this proposal. We also contrast this state with a "noncollinear" nematic state proposed earlier by Tsunetsugu and Arikawa [J. Phys. Soc. Jpn. 75, 083701 (2006)] for NiGa2S4