Hybridization at metal/oxide interfaces to understand Dzyaloshinskii–Moriya interaction in asymmetrically sandwiched thin films of binary alloys

磁性薄膜和多层膜中手性相互作用的研究是现代磁学研究的前沿。最近，表面诱导的Dzyaloshinskii-Moriya相互作用(DMI)被证明提供了一种在室温下稳定手性Skyrmion和Skyrmion气泡的方法，从而为存储器和逻辑器件的新应用铺平了道路。典型的材料系统通常由夹在两个重金属(HM)层或一个HM和一个金属氧化物(MO)层之间的薄铁磁性(FM)层组成。精确设计MO/FM/HM接口的能力为设计可行的旋转轨道电子器件提供了一个令人兴奋的选择。除了界面的影响外，还应考虑其他影响DMI强度的因素，如原子构型、界面质量和本征磁性参数。在这个项目中，我们的目标是将界面DMI的强度与界面上电子态的杂化水平相关联。我们的主要重点是研究包含二元合金的层叠，包括夹在重金属(铂或钽)和金属氧化物(AlOx和CrOx)之间的FePT、CoPt和MnAl。关于合金薄膜的结果将与基于非对称夹层钴层的参照系进行比较。这项工作主要是试验性的。我们将探索不同的方法来评估典型超薄层堆栈界面上的电子态杂化。为了解决这一任务，我们将使用不同的技术，包括X射线光电子能谱(XPS)和扫描俄歇电子能谱(Nano-Auger)与二次中性质谱仪(SNMS)相结合，以了解哪种方法(或方法组合)最适合解决界面上的电子修饰。此外，我们将探索不同的方法来确定DMI强度，包括使用布里渊光散射(BLS)测量非对称自旋波色散，监测磁光Kerr显微镜中的磁畴图案的演变，以执行自旋轨道扭矩测量。这些实验数据将与理论小组合作进行分析，以提供复杂多层异质结构中手性效应的定量描述。在这方面，该项目的结果将对广泛的自旋电子学和自旋轨道电子学社区具有重要意义。

The study of chiral interactions in magnetic thin films and multilayers is at the forefront of the modern magnetism research. Very recently, surface-induced Dzyaloshinskii-Moriya interaction (DMI) was proven to provide a way to stabilize chiral skyrmions and skyrmion bubbles at room temperature, thus paving the way towards novel application ideas for memory and logic devices. Typical material systems are generally comprised of a thin ferromagnetic (FM) layer sandwiched between two heavy metal (HM) layers or one HM and a metal oxide (MO) layer. The ability to precisely engineer the MO/FM/HM interfaces offers an exciting option to design viable spinorbitronic devices. In addition to the impact from interfaces, other factors influencing the DMI strength, such as atomic configuration, interface quality, and intrinsic magnetic parameters, should be taken into account. In this project, we aim to correlate the strength of interfacial DMI with the level of hybridization of electronic states at the interfaces. Our primary focus is to study layer stacks containing binary alloys including FePt, CoPt and MnAl sandwiched between heavy metal (Pt or Ta) and metal oxide (AlOx and CrOx). The results on alloys films will be compared to a reference system based on asymmetrically sandwiched Co layers. The work is primarily experimental. We will explore different methods to assess the hybridization of electronic states at the interfaces of typically ultrathin layer stacks. To address this task we will use different techniques including X-ray Photoelectron Spectroscopy (XPS) and scanning Auger Electron Spectroscopy (nano-Auger) combined with Secondary Neutral Mass Spectrometer (SNMS) to understand, which method (or combination of methods) is the most appropriate to address the electronic modifications at the interfaces. Furthermore, we will explore different methods to determine the DMI strength, including measurement of asymmetric spin wave dispersion using Brillouin light scattering (BLS), monitoring the evolution of magnetic domain patterns in magnetooptical Kerr microscopy of performing spin orbit torques measurements. These experimental data will be analyzed in collaboration with theory groups to provide quantitative description of chiral effects in complex multilayered heterostructures. In this respect, the results of this project will be of relevance for broad spintronics and spinorbitronics communities.