LiCrSe₂ constitutes a recent valuable addition to the ensemble of two-dimensional triangular lattice antiferromagnets. In this work, we present a comprehensive study of the low temperature nuclear and magnetic structure established in this material. Being subject to a strong magnetoelastic coupling, LiCrSe₂ was found to undergo a first order structural transition from a trigonal crystal system (\(P\bar{3}m1\)) to a monoclinic one (C2/m) at T_s = 30 K. Such restructuring of the lattice is accompanied by a magnetic transition at T_N = 30 K. Refinement of the magnetic structure with neutron diffraction data and complementary muon spin rotation analysis reveal the presence of a complex incommensurate magnetic structure with a up-up-down-down arrangement of the chromium moments with ferromagnetic double chains coupled antiferromagnetically. The spin axial vector is also modulated both in direction and modulus, resulting in a spin density wave-like order with periodic suppression of the chromium moment along the chains. This behavior is believed to appear as a result of strong competition between direct exchange antiferromagnetic and superexchange ferromagnetic couplings established between both nearest neighbor and next nearest neighbor Cr³⁺ ions. We finally conjecture that the resulting magnetic order is stabilized via subtle vacancy/charge order within the lithium layers, potentially causing a mix of two co-existing magnetic phases within the sample.

LiCrSe ₂是二维三角晶格反铁磁体中最新的有价值的补充。在这项工作中，我们对这种材料中建立的低温核和磁结构进行了全面的研究。由于受到强磁弹性耦合，LiCrSe _2在T _s时经历了从三方晶系 ( \(P\bar{3}m1\) ) 到单斜晶系 ( C 2/ m )的一级结构转变 = 30 K。这种晶格重组伴随着T _{N处的磁转变} = 30 K。利用中子衍射数据和互补μ子自旋旋转分析对磁结构进行细化，揭示了存在复杂的不相称磁结构，其中铬矩具有上下排列，铁磁双链反铁磁耦合。自旋轴向矢量的方向和模量也受到调制，从而产生自旋密度波状有序，并沿着链周期性抑制铬矩。这种行为被认为是最近邻和次近邻 Cr ^{3+之间建立的直接交换反铁磁耦合和超交换铁磁耦合之间强烈竞争的结果。}离子。我们最终推测，所产生的磁序通过锂层内微妙的空位/电荷序来稳定，可能导致样品内两个共存磁相的混合。