Valentine Michael E, Higo Tomoya, Nambu Yusuke, Chaudhuri Dipanjan, Wen Jiajia, Broholm Collin, Nakatsuji Satoru, Drichko Natalia
Institute for Quantum Matter and Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218, USA.
Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581, Japan.
Phys Rev Lett. 2020 Nov 6;125(19):197201. doi: 10.1103/PhysRevLett.125.197201.
NiGa_{2}S_{4} is a triangular lattice S=1 system with strong two dimensionality of the lattice, actively discussed as a candidate to host spin-nematic order brought about by strong quadrupole coupling. Using Raman scattering spectroscopy we identify a phonon of E_{g} symmetry which can modulate magnetic exchange J_{1} and produce quadrupole coupling. Additionally, our Raman scattering results demonstrate a loss of local inversion symmetry on cooling, which we associate with sulfur vacancies. This will lead to disordered Dzyaloshinskii-Moriya interactions, which can prevent long-range magnetic order. Using magnetic Raman scattering response we identify 160 K as a temperature of an upturn of magnetic correlations. The temperature range below 160 K, but above 50 K where antiferromagnetic correlations start to increase, is a candidate for spin-nematic regime.
NiGa₂S₄是一种具有强烈晶格二维性的三角晶格S = 1系统，作为由强四极耦合引起的自旋向列序的宿主候选物而受到积极讨论。利用拉曼散射光谱，我们识别出一种具有E₉对称性的声子，它可以调制磁交换J₁并产生四极耦合。此外，我们的拉曼散射结果表明，冷却时局部反演对称性丧失，我们将其与硫空位联系起来。这将导致无序的Dzyaloshinskii-Moriya相互作用，从而阻止长程磁序。利用磁拉曼散射响应，我们确定160 K为磁关联上升的温度。160 K以下但高于50 K（反铁磁关联开始增加的温度）的温度范围是自旋向列相的候选区域。
