X-ray specular and off-specular diffuse scattering of magnetic interface structures at XFEL sources - investigating ultrafast spin transport processes

最近在fs时间尺度上的实验揭示了磁性多层系统中不寻常的猝灭机制，这暗示了伴随退磁过程的空间成分。目前，这被解释为通过磁性材料和跨界面产生超快自旋相关输运过程的超快自旋扩散过程。我们想用反射几何中的软x射线和XUV辐射来研究这种磁性界面。这种散射几何可以绘制出磁性多层系统界面和表面的电荷和自旋密度分布图，并确定对自旋系统变化特别敏感的互易空间中的位置。利用XFELs，我们想测量在超短红外激光脉冲照射下界面结构的自旋和电荷分布的时间分辨演化。实验将研究跨界面结构的超快自旋扩散过程的细节。反射率产生垂直自旋密度剖面的细节，而漫射散射通道允许以深度分辨的方式跟踪平行于界面的磁相关长度。因此，我们希望绘制出在超短激光脉冲照射下磁性多层体系的完整可用q空间，并跟踪相应的自旋密度分布的时空演变。该结果将为自旋扩散和跨磁界面结构输运过程的物理学提供独特的见解。

Recent experiments on fs time scales revealed unusual quenching mechanisms in magnetic multilayer systems, which hint towards a spatial component accompanying the demagnetization process. This is currently interpreted in terms of ultrafast spin-diffusion processes through magnetic materials and across interfaces yielding an ultrafast spin-dependent transport process. We want to study such magnetic interfaces using soft X-ray and XUV radiation in reflection geometry. This scattering geometry allows to map out the charge and spin density profiles of interfaces and surfaces of magnetic multilayer systems and to identify positions in reciprocal space being particular sensitive to changes in the spin-system. Using XFELs in the XUV regime we want to measure time resolved the evolution of spin and charge profiles across interface structures upon irradiation with an ultra-short IR laser pulse. The experiments shall investigate details of the ultrafast spin diffusion processes across interface structures. Reflectivity yields details of the perpendicular spin density profile while the diffuse scattering channels allow to follow magnetic correlation lengths parallel to the interface in a depth resolved manner. Thus we want to map out the full available Q-space of magnetic multilayer systems upon irradiation with an ultrashort laser pulse and follow the space and time evolution of the corresponding spin density profiles. The results will give unique insights into the physics of spin diffusion and transport processes across magnetic interface structures.