New high magnetic field phase of the frustrated S=1/2 ferromagnetic chain LiCuVO4

Magnetization of the frustrated S=1/2 ferromagnetic chain cuprate LiCuVO4, focusing on the high magnetic field phases, is reported. Besides a spin-flop transition and the transition from a planar spiral to a spin modulated structure observed recently, an additional transition was observed just below the saturation field. This newly observed magnetic phase is considered as a spin nematic phase, which was predicted theoretically but was not observed experimentally. The lower and upper critical fields of this phase are in good agreement with those calculated by Zhitomirsky and Tsunetsugu using a microscopic model (M. E. Zhitomirsky and H. Tsunetsugu, preprint, arXiv:1003.4096v1).