Magnetic structure of a frustrated honeycomb-lattice antiferromagnet, CaMn2As2.

We wish to perform neutron powder diffraction measurements on triturated crystals of a frustrated honeycomb-lattice antiferromagnet, CaMn2As2, at temperatures below and above its magnetic phase transition at TN = 62 K. We expect to collect data suitable for solving the low-T magnetic structure of CaMn2As2 and also for exploring its magnetic behavior above TN. Our interest in this material was simulated by reports indicating that an isostructural and isoelectronic compound, CaMn2Sb2, is located close to a tricritical point known for the J1-J2-J3 classical Heisenberg model of spins on a honeycomb lattice. Near this point, the Néel phase and two different spiral phases become degenerate and therefore strong magnetic frustration is expected. While CaMn2Sb2 adopts the Néel phase, for CaMn2As2 an incommensurate spiral magnetic structure is suspected based on the recently reported 75As nuclear magnetic resonance study. The accurate determination of the low-temperature magnetic ordering in CaMn2As2 is the primary goal of the proposed experiment. The expected results will be used to locate this compound on the Heisenberg phase diagram, they will inform theoretical studies and guide our doping attempts aiming at inducing a spin liquid state.

本研究拟对受挫蜂窝晶格反铁磁体CaMn₂As₂的研碎晶体开展中子粉末衍射（neutron powder diffraction）测量，测量温区覆盖其磁相变温度TN=62 K上下。我们期望采集到适用于解析CaMn₂As₂低温磁结构的实验数据，同时亦可探索其奈尔温度以上的磁学行为。
我们对该材料的研究兴趣源于相关报道：同构等电子化合物CaMn₂Sb₂处于蜂窝晶格自旋的J1-J2-J3经典海森堡模型（J1-J2-J3 classical Heisenberg model）所预言的三临界点附近。在此临界点附近，奈尔相与两种不同的螺旋磁相简并，因此体系将呈现出较强的磁受挫效应。已有研究证实CaMn₂Sb₂为奈尔相结构，而基于近期发表的75As核磁共振（75As nuclear magnetic resonance）研究，我们推测CaMn₂As₂具有非公度螺旋磁结构。
本拟开展实验的首要目标是精准确定CaMn₂As₂的低温磁有序结构。预期获得的实验结果将用于定位该化合物在海森堡相图（Heisenberg phase diagram）中的位置，可为相关理论研究提供支撑，并指导我们后续旨在诱导自旋液态（spin liquid state）的掺杂尝试。

搜集汇总

背景与挑战

背景概述

该数据集包含通过ISIS中子与μ子源的WISH仪器收集的中子粉末衍射数据，专注于研究受挫蜂窝晶格反铁磁体CaMn2As2的磁性结构。实验旨在确定材料在低温下的磁有序相，并探索其高于磁相变温度（TN = 62 K）的磁行为，以帮助定位其在海森堡相图中的位置。数据集当前未公开，计划于2027年3月17日发布，数据格式为RAW/Nexus，适用于磁性材料和凝聚态物理研究。