Authors: Masahiro Sato, Toshiya Hikihara, and Tsutomu Momoi
Magnetic multipolar order, especially, quadrupolar (spin nematic) order, is one of the current topics in frustrated magnetism. Recently, frustrated spin-1/2 chains with ferromagnetic nearest neighbor J1(<0) and antiferromagnetic next nearest neighbor J2(>0) couplings have been theoretically shown to exhibit a spin nematic quasi long range order in a broad range of J1/J2 as external magnetic field is applied [1,2]. In addition, magnetic properties of several quasi one-dimensional (1D) cuprate magnets  are believed to be described by this J1-J2 spin chain model [1,2,4,5]. In particular, recent experiments show that LiCuVO4, one of the quasi-1D cuprates, possesses a new phase near saturation, and it is expected to be a 3D spin nematic ordered phase [6,7]. Motivated by these results, we have developed a general theory of the spin nematic ordering  for 3D spatially anisotropic magnets consisting of weakly coupled J1-J2 spin chains, combining the field theoretical technique [1,4] with numerical results. We have completed the phase diagram in a wide temperature and magnetic-field ranges. The phase diagram contains both spin nematic and spin-density-wave ordered phases, and these two orders compete with each other. We will discuss some universal features of the phase diagram and the relevance of our result to LiCuVO4.
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M.Sato, T.Momoi, and A.Furusaki, PRB79, 060406(R) (2009); M.Sato, T.Hikihara, and T.Momoi, PRB83, 064405 (2011).
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L.E.Svistov, et al, JETP Lett. 93, 21 (2011).
M. Mourigal, et al, PRL109, 027203 (2012).
M.Sato, T.Hikihara, and T.Momoi, arXiv:1208.2235.
Author entry (protected)