Department of Physics, 500 W University Ave, The University of Texas at El Paso, El Paso, TX 79968, USA.
Institute of Physics, Bijenička cesta 46, HR-10000, Zagreb, Croatia.
Dalton Trans. 2023 May 2;52(17):5652-5662. doi: 10.1039/d3dt00052d.
The Mn lattice in olivine chalcogenide MnSiX (X = S, Se) compounds forms a sawtooth, which is of special interest in magnetism owing to the possibility of realizing flat bands in magnon spectra, a key component in magnonics. In this work, we investigate the MnSiX olivines using magnetic susceptibility, and X-ray and neutron diffraction. We have determined the average and local crystal structures of MnSiS and MnSiSe using synchrotron X-ray, neutron diffraction, and X-ray total scattering data followed by Rietveld and pair distribution function analyses. It is found from the pair distribution function analysis that the Mn triangle that constitutes the sawtooth is isosceles in MnSiS and MnSiSe. The temperature evolution of magnetic susceptibility of MnSiS and MnSiSe shows anomalies below 83 K and 70 K, respectively, associated with magnetic ordering. From the neutron powder diffraction measurements the magnetic space groups of MnSiS and MnSiSe are found to be and '', respectively. We find that the Mn spins adopt a ferromagnetic alignment on the sawtooth in both MnSiS and MnSiSe but along different crystallographic directions for the S and the Se compounds. From the temperature evolution of Mn magnetic moments obtained from refining neutron diffraction data, the transition temperatures are accurately determined as (S) = 83(2) K and (Se) = 70.0(5) K. Broad diffuse magnetic peaks are observed in both the compounds, and are prominently seen close to , suggesting the presence of a short-range magnetic order. The magnetic excitations studied using inelastic neutron scattering reveal a magnon excitation with an energy corresponding to approximately 4.5 meV in both S and Se compounds. Spin correlations are observed to persist up to 125 K much above the ordering temperature and we suggest the possibility of short-range spin correlations responsible for this.
橄榄石型硫属化物 MnSiX（X=S，Se）化合物中的 Mn 晶格呈锯齿状，由于在磁振子谱中实现平带的可能性，这种锯齿状结构在磁性方面具有特殊意义，而平带是磁振子学的关键组成部分。在这项工作中，我们使用磁化率、X 射线和中子衍射研究了 MnSiX 橄榄石。我们使用同步加速器 X 射线、中子衍射和 X 射线总散射数据以及 Rietveld 和配分函数分析确定了 MnSiS 和 MnSiSe 的平均和局部晶体结构。从配分函数分析中发现，构成锯齿状的 Mn 三角形在 MnSiS 和 MnSiSe 中是等腰三角形。MnSiS 和 MnSiSe 的磁化率随温度的演化分别在 83 K 和 70 K 以下出现异常，与磁有序有关。从中子粉末衍射测量结果可知，MnSiS 和 MnSiSe 的磁空间群分别为 和 ''。我们发现，Mn 自旋在 MnSiS 和 MnSiSe 中的锯齿上呈铁磁排列，但对于 S 和 Se 化合物，其排列方向沿不同的晶体学方向。从通过 refinement 中子衍射数据获得的 Mn 磁矩的温度演化中，准确地确定了转变温度为 (S) = 83(2) K 和 (Se) = 70.0(5) K。在这两种化合物中都观察到宽的漫散射磁峰，并且在接近 时特别明显，表明存在短程磁有序。使用非弹性中子散射研究的磁激发显示出在 S 和 Se 化合物中具有约 4.5 meV 能量的磁振子激发。观察到自旋相关性在远高于有序温度的 125 K 以上仍然存在，我们认为这可能是短程自旋相关性造成的。
