Novel geometrical frustration effects in the two-dimensional triangular-lattice antiferromagnet NiGa2S4 and related compounds

Satoru Nakatsuji, Yusuke Nambu, Shigeki Onoda

Research output: Contribution to journalArticlepeer-review

40 Citations (Scopus)


Geometrical frustration may suppress conventional magnetic long-range order and possibly promote a novel type of ordering associated with a higher order degree of freedom than spin dipolar-moment such as vector spin chirality and spin quadrupole moment. After a brief overview of such phenomena due to vector spin chirality, we focus on the two-dimensional (2D) frustrated magnetism in the layered chalcogenide Mott insulator NiGa2S4 and related compounds. NiGa2S4 provides the unique example of a S = 1 2D antiferromagnet on a regular exact triangular lattice. Extensive studies using high-purity samples of NiGa2S4 have revealed that Ni2+ S = 1 Heisenberg spins exhibit resonant critical slowing down at T*= 8:5K without forming a magnetic long-range order, signaling a viscous spin-liquid state. The critical spin-fluctuation regime extends over almost an order of magnitude in temperature both above and below T* . Even well below T*, the spin-spin correlation remains short-ranged at an incommensurate wave vector close to (1/6, 1/6, 0), corresponding to a 120° correlation with 2a period. Interestingly, however, a 2D linearly dispersive magnetic mode and a quasi-static spin component exist in the low temperature limit. Possibly relevant scenarios including topological phase transition associated with Z2 vortex due to vector spin chirality, spin quadrupolar nematic correlation, and C 3 bond-ordering are reviewed.

Original languageEnglish
Article number011003
Journaljournal of the physical society of japan
Issue number1
Publication statusPublished - 2010 Jan
Externally publishedYes


  • C bond-order
  • Critical slowing down
  • Nigas
  • Spin nematic
  • Spin quadrupole moment
  • Triangular lattice
  • Vector spin chirality
  • Viscous spin liquid

ASJC Scopus subject areas

  • Physics and Astronomy(all)


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