Investigations of spin currents in elemental, alloyed and multilayer systems using spin-torque ferromagnetic resonance technique

Abstract

Current-induced spin-orbit torques (SOT) are a vital research field within the realm of spintronics. They have attracted significant attention due to the vast opportunities for applications, e.g., in neuromorphic computing or memory devices, and their potential to reduce energy consumption in said applications. Energy efficient generation of SOT is an enormous "[…] after all you put me through, You'd think I'd despise you, But in the end, I wanna thank you, 'Cause you made me that much stronger" [1]. These words from Christina Aguilera's song "Fighter" summarize nicely how this Ph.D. journey has felt. It has been an arduous journey with many ups and downs, but it was a challenge that was always meant to be conquered and grow from. However, it also was never supposed to be a solo trip, and luckily, I didn't have to do this all on my own but with the support of great people from all over the world: Firstly, I thank Prof Lew Wen Siang for giving me the opportunity to conduct my research under your supervision. I also thank you for your support and advice throughout my Ph.D. journey.Next, I thank all group members, past and present, for support of all kinds and an enjoyable work environment. In particular, I like to give some shoutouts to the following people: Gerard, thank you for your help with every detail in the lab and beyond. Thank you for ensuring that everything runs smoothly. Weiliang, thank you for building the first laser litho in our lab, significantly shortening my sample fabrication time. Also, for your help with my first paper, general support, and enlightening discussions. Grayson, for your introduction to ST-FMR measurement techniques and analysis and EBL and other equipment in the lab. Xu Zhan, or as you were introduced to me: "Bob", for your help with my first project and for sharing your knowledge about spintronics and ST-FMR. Wai Cheung, thank you for your help with ST-FMR measurements, even after you left NTU, and for helping me even, when I wasn't aware of it. Calvin Ang, thank you for introducing sputtering and answering my random questions.Jia Min, for proofreading my emails, printing my documents, and sharing your love for breaks and your emotional support. And speaking of emotional support, Lingli and Andhita, thank you both for your friendship, the more or less spontaneous hiking trips, and most importantly, lunch and dinner chats. Andhita, thanks for partly sharing my enthusiasm for running and podcasts and your consistently good mood. Tianli, thank you for being a great desk neighbor; those late nights would have been very lonely without you. And thank you for answering my questions whenever they come up. Funan, thank you for your help with my research, even when it was not your expertise, and for your help with whatever came up. And please say thank you to your mom for preparing the fruit box, which you generously shared with your teammates. Han Yin,