报告题目：Spin-orbit technologies: memory switching to THz generation
报告人：Hyunsoo Yang（Department of Electrical and Computer Engineering, National University of Singapore）
Current induced spin-orbit torques (SOTs) provide a new way to manipulate the magnetization. We first try to understand various spin textures. In order to probe spin textures, we utilize the bilinear magnetoelectric resistance, photovoltage microscopy for topological insulators, and Lorentz transmission electron microscopy for imaging of chiral spin textures, skyrmions in an exchange-coupled Co/Pd multilayer.
We then utilize those spin textures for magnetization switching. We find that a full sign reversal of SOTs occurs as the oxygen bonding increases in Pt/CoFeB/MgO, which evidences an interfacial SOT mechanism. We show much enhanced current induced SOTs from Co/Pd multilayers , ferrimagnetic CoGd systems , a topological insulator Bi2Se3 as well as an oxide heterostructure SrTiO3/LaAlO3 , which generate strong spin currents to switch the magnetization. In order to understand detailed switching SOT switching mechanism, time resolved SOT spin dynamics is probed, and oscillatory SOT switching induced by field-like torques is measured. We propose a field-free SOT switching scheme using one domain wall motion in an anti-notch structure. Finally, we discuss the generation of THz for heavy metal/ferromagnet structures using SOTs.
Hyunsoo Yang worked at C&S technology, LG Electronics in San Jose, and Intelligent Fiber Optic Systems, California after his Bachelor degree from Seoul National University in Korea. He received his Master and Doctorate from Stanford University. He worked on optoelectronic devices for fiber communication at Stanford University. From 2004-2007, he was at IBM-Stanford Spintronic Science and Applications Center with Dr. Stuart Parkin. He is currently a Globalfoundries Chaired associate professor in the Department of Electrical and Computer Engineering, National University of Singapore (NUS), and working on various magnetic materials and devices for spintronics applications.
Prof. Yang has authored 170 journal articles in peer-reviewed journals, including book chapters and invited review articles. He has given more than 100 invited presentations and hold 15 issued patents on spintronics, magnetism, device physics, nano-materials, topological devices, and optoelectronics. He has won several awards including an Outstanding Dissertation Award for 2006 from the American Physical Society (GMAG) and IEEE Magnetics Society
Distinguished Lecturers for 2019.