Wei Yuan, Tseng Yi, Elnaggar Hebatalla, Zhang Wenliang, Asmara Teguh Citra, Paris Eugenio, Domaine Gabriele, Strocov Vladimir N, Testa Luc, Favre Virgile, Di Luca Mario, Banerjee Mitali, Wildes Andrew R, de Groot Frank M F, Rønnow Henrik M, Schmitt Thorsten
PSI Center for Photon Science, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland.
Laboratory for Quantum Magnetism, Institute of Physics, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland.
NPJ Quantum Mater. 2025;10(1):61. doi: 10.1038/s41535-025-00777-0. Epub 2025 Jun 17.
Van der Waals (vdW) materials are featuring intertwined electronic order and collective phenomena. Elucidating the dynamics of the elementary excitations within the fundamental electronic degrees of freedom is of paramount importance. Here we performed resonant inelastic X-ray scattering (RIXS) to elaborate the spin-orbital excitations of the vdW antiferromagnet FePS and their role for magnetism. We observed the spectral enhancement of spin-orbital multiplet excitations at about ~100 and ~220 meV, as well as the quasielastic response, when entering the antiferromagnetic phase with an order-parameter-like evolution in temperature. By comparing with model calculations, we discovered the trigonal lattice distortion, spin-orbit interaction and metal-ligand charge-transfer to be essential for these emergent excitations. We further reveal their spectral robustness down to the few atomic-layer limit by mechanical exfoliation, in accordance with the persistent antiferromagnetism reported previously. Our study highlights the crucial role of lattice and orbital anisotropy for stabilizing the quasi-two-dimensional magnetism and tailoring vdW magnets.
范德华（vdW）材料具有相互交织的电子序和集体现象。阐明基本电子自由度内元激发的动力学至关重要。在此，我们进行了共振非弹性X射线散射（RIXS），以详细研究范德华反铁磁体FePS的自旋 - 轨道激发及其在磁性中的作用。我们观察到，在进入反铁磁相时，随着温度呈现类似序参量的演化，在约100和约220毫电子伏特处自旋 - 轨道多重态激发的光谱增强以及准弹性响应。通过与模型计算进行比较，我们发现三角晶格畸变、自旋 - 轨道相互作用和金属 - 配体电荷转移对于这些新出现的激发至关重要。根据先前报道的持续反铁磁性，我们通过机械剥离进一步揭示了它们在低至几个原子层极限时的光谱稳健性。我们的研究突出了晶格和轨道各向异性在稳定准二维磁性和定制范德华磁体方面的关键作用。
