TY - JOUR
T1 - Novel geometrical frustration effects in the two-dimensional triangular-lattice antiferromagnet NiGa2S4 and related compounds
AU - Nakatsuji, Satoru
AU - Nambu, Yusuke
AU - Onoda, Shigeki
N1 - Copyright:
Copyright 2010 Elsevier B.V., All rights reserved.
PY - 2010/1
Y1 - 2010/1
N2 - 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.
AB - 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.
KW - C bond-order
KW - Critical slowing down
KW - Nigas
KW - Spin nematic
KW - Spin quadrupole moment
KW - Triangular lattice
KW - Vector spin chirality
KW - Viscous spin liquid
UR - http://www.scopus.com/inward/record.url?scp=77049119739&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=77049119739&partnerID=8YFLogxK
U2 - 10.1143/JPSJ.79.011003
DO - 10.1143/JPSJ.79.011003
M3 - Article
AN - SCOPUS:77049119739
VL - 79
JO - Journal of the Physical Society of Japan
JF - Journal of the Physical Society of Japan
SN - 0031-9015
IS - 1
M1 - 011003
ER -