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

• Applicants: Dr. Denys Makarov; Privatdozentin Dr. Elena Vedmedenko
• Subject Area: Experimental Condensed Matter Physics ; Theoretical Condensed Matter Physics
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 514141286

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.

• DFG Programme: Research Grants
• International Connection: Ukraine
• Co-Investigator: Dr. Stefan Facsko
• International Co-Applicant: Dr. Igor Vladymyrskyi