Time： July 24, 2018（Tuesday），14:00-16:00
Place：Room 318，11th teaching building ，Yuquan Campus
Title：Electric Current Induced Magnetization Reversal
Speaker：Dr Jingsheng CHEN,Department of Materials Science and Engineering, National University of Singapore
Inviter：Prof He TIAN
Bio：
Dr Jingsheng Chen is an Associate Professor in Department of Materials Science and Engineering. He obtained his Ph.D degree in 1999 in Lanzhou University, China and joined NUS in December 2007. During 2001-2007 he worked at the Data Storage Institute as a research scientist. He has authored/co-authored more than 240 refereed journal papers, 3 book chapters, holds over ten patents and has made more than 50 invited presentation in the international conferences. His research work has obtained more than 4000 non-self-citations with H index of 35. His research interest includes magnetic and oxide based non-volatile memories, spintronics, ferroelectric tunnel junction, strongly correlated oxide materials. He secured more than S$15 million research grants from government and around US$ 800k from Seagate Technology and more than S$ 1 million from Globalfoundries. The magnetic recording media in the newest generation of HDD (HAMR) applied a few of his inventions.
Abstract：
Electrical manipulation of magnetization is essential for integration of magnetic functionalities such as magnetic memories and magnetic logic devices into electronic circuits. The current induced spin-orbit torque (SOT) in heavy metal/ferromagnet (HM/FM) bilayers via the spin Hall effect in the HM and/or the Rashba effect at the interfaces provides an efficient way to switch the magnetization. In this talk, I will present the following research activities in my group; (1) Emergence of Gilbert damping anisotropy in LaSrMnO3 thin films; (2) Giant Anisotropic Spin-Hall angle in collinear antiferromagnets, (3) Tuning the Rashba effects by using multiferroic heterostructure (4) Current induced SOT switching in a single magnetic layer with centrosymmetry. I will discuss the part (4) in more details. It has also been observed in ferromagnetic semiconductor (Ga,Mn)As and antiferromagnetic metals CuMnAs and Mn2Au with globally or locally broken inversion symmetry, respectively. Here we demonstrate the current induced magnetization switching in a single ferromagnetic layer, L10 FePt, with centrosymmetric crystal structure. The spin-orbit effective fields increase with the chemical ordering of L10 FePt films. In 20 nm FePt films with higher chemical ordering, we observe a surprisingly large charge-to-spin conversion efficiency (3.4), which is one order of magnitude larger than that in HM/FM bilayers. In addition, we find the switching current density of the 20 nm FePt film as low as 7.0×106 A/cm2. We anticipate our findings may stimulate the exploration of the spin-orbit torques in centrosymmetric materials and the application of high-efficient perpendicular magnetization switching in single FM layer.
