Element specific spin dynamics of nano- and heterostructues studied with ultimate spatial resolution

本提案的目的是利用一种新的实验工具，对复杂磁环境中单个磁性微纳米物体的动态磁性进行系统的研究，该实验工具是申请人与斯坦福同步辐射实验室（SSRL）的光束线工作人员共同开发的。这种独特的新型仪器结合了基于x射线磁圆二分性（XMCD）的元素特异性磁性研究，其横向空间分辨率为35 nm的扫描透射x射线显微镜（STXM），以及低至17 ps的时间分辨检测方案，允许研究具有空间分辨率的时间分辨横向x射线检测铁磁共振（XFMR）。微波激发是基于在SiN膜上平版制造的微谐振器，所讨论的磁性微或纳米物体将被放置在其中。这些微谐振器的使用提供了一个独特的机会，可以同时研究传统的FMR信号，该信号在磁系综上平均，以及每个单独纳米成分的空间分辨XFMR响应。我们的目标是进行以下一系列的实验：1。微纳米条纹中均匀和非均匀自旋波激发的空间成像和时间分辨相位信息，其中激发模式由结构的形状或邻近铁磁结构产生的局部杂散场改变。这些局部场可以用来增强或抑制局部激励。计划用于结构的材料将是Co作为硬材料和Permalloy （Py）作为软磁材料。利用单个铁或氧化铁纳米颗粒研究在磁耦合或局部杂散场影响下单个纳米颗粒的局部动态磁性能。在微磁模拟的支持下，可以通过排列不同几何形状和/或数量的纳米颗粒来定制磁激发态。3. 利用STXM-FMR的元素特异性、空间和时间分辨率，直接成像异质结构中自旋泵浦产生的非磁性材料中的自旋电流。将低自旋轨道耦合材料（如ZnO或Al）上的Py微条纹驱动到FMR中，并对产生的自旋电流的空间分布和相对相位进行成像。

The aim of this proposal is to carry out a systematic investigation of the dynamic magnetic properties of individual magnetic micro- and nano-objects in a complex magnetic environment utilizing a novel experimental tool, which the applicants jointly developed with the beamline staff of the Stanford Synchrotron Radiation Laboratory (SSRL). This rather unique novel instrument combines element specific investigation of the magnetic properties based on X-ray magnetic circular dichoism (XMCD) with the lateral spatial resolution of nominally 35 nm of the scanning transmission x-ray microscope (STXM) as well as a time-resolved detection scheme down to 17 ps allowing to study time-resolved transversal x-ray detected ferromagnetic resonance (XFMR) with spatial resolution. The microwave excitation is based on lithographically fabricated micro-resonators on SiN membranes into which the magnetic micro- or nano-object in question will be placed. The use of these microresonators provides the unique opportunity to simultaneously investigate the conventional FMR signal which averages over the magnetic ensemble and the space resolved XFMR response of each individual nano constituent. We aim at pursuing the following range of experiments:1. spatial imaging and time resolved phase information of uniform and non-uniform spinwave excitations in micro- and nanostripes where the excitation modes are modified by the shape of the structures or by local stray-fields generated by adjacent ferromagnetic structures. These local fields can be used to enhance or suppress local excitations. Planned materials for the structures will be Co as hard and Permalloy (Py) as soft magnetic material.2. investigations of local dynamic magnetic properties of individual nanoparticles under the influence of magnetic coupling or local stray fields in an ensemble using individual Fe or Fe oxide nanoparticles. The magnetic excitation states can be tailored by arranging the nano particles in different geometries and/or number backed by micro magnetic simulations. 3. direct imaging of spin currents in a non-magnetic material generated by spin-pumping in hetero structures utilizing the element specificity, space- and time-resolution of the STXM-FMR. A Py microstripe on top of a low spin-orbit coupling material like ZnO or Al shall be driven into FMR and the spatial distribution and relative phase of the generated spin current will be imaged.