Lattice instability in antiferromagnetic B2 FeRh

With this experiment, we want to investigate the theoretically predicted lattice instability in AFM FeRh in the B2 structure. In preliminary Fe K-edge EXAFS measurements, we observed the occurrence of a lattice distortion that can be modelled by assuming a B2-lattice with slight lattice distortions predicted by Wolloch et al. With the experiment, we want to investigate the local surrounding of the Fe and Rh atoms by EXAFS. Complementary, we plan to investigate the structural lattice instability by X-ray diffraction to further corroborate our spectroscopy results. As a last step, we aim at performing temperature-dependent measurements focussing on the lattice dynamics to investigate changes on the local surrounding around the Fe and Rh atoms (EXAFS) and the long-range order (XRD). Here, we specially want to investigate the effects and possible different structural response of the dynamically stabilised lattice instability on the short range, as well as on the long-range order.

本实验旨在研究B2结构反铁磁（Antiferromagnetic，AFM）铁铑（FeRh）体系中理论预测的晶格不稳定性。在前期铁K边扩展X射线吸收精细结构谱（Extended X-ray Absorption Fine Structure，EXAFS）测试中，我们观测到了晶格畸变现象，该畸变可通过采用Wolloch等人预测的含轻微晶格畸变的B2晶格模型进行拟合。本次实验将通过EXAFS表征铁与铑原子的局域配位环境。作为补充表征，我们计划采用X射线衍射（X-ray Diffraction，XRD）研究结构晶格不稳定性，以进一步佐证光谱学测试结果。最后，我们将开展温度依赖型测试，重点聚焦晶格动力学，以探究铁、铑原子局域配位环境（通过EXAFS表征）与长程有序性（通过XRD表征）的变化情况。在此过程中，我们将专门研究动态稳定化晶格不稳定性在短程与长程有序尺度上产生的影响，以及可能出现的不同结构响应。