Triangular antiferromagnet NiGa2S4: a low-dimensional analog of the pyrochlores?

NiGa2S4 is a frustrated magnet on a triangular lattice with a strong antiferromagnetic third-neighbor exchange J3 and a weak ferromagnet first-neighbor exchange J1. Although the system has been studied for more than a decade [1], its behavior, particularly the lack of long-range order, remains enigmatic. Exotic scenarios have been proposed for its explanation, including the formation of a quadrupolar spin order that cannot be seen by the usual probes like neutrons [2]. We propose a different scenario based on a simple observation: the 4-sublattice structure resulting from a strong J3 makes the system similar to a pyrochlore antiferromagnet. The geometrical frustration of the pyrochlore antiferromagnet can be relieved by a lattice distortion [3]. A similar tendency may exist in NiGa2S4. The spin-Peierls phase transition may be preempted by structural disorder involving random strains.


[1] S. Nakatsuji, Science 309, 1697 (2005).

[2] A. Läuchli, F. Mila, and K. Penc, Phys. Rev. Lett. 97, 467 (2006).

[3] O. Tchernyshyov, R. Moessner, and S. L. Sondhi, Phys. Rev. B 66, 357 (2002).