Professor Kelly Luo
University of Southern California
Spin-orbit torque in magnetic van der Waals heterostructures: exchange interactions and non-uniform spin ordering
Location: 1080 Physics Research Building
Faculty Host: Roland Kawakami
Abstract: Spin-orbit torques provide the most efficient mechanism known for reliably manipulating the magnetic orientation of nanomagnets, and are therefore both of fundamental scientific interest and of technological interest for next-generation magnetic memories. van der Waals (vdW) magnets have emerged as an exciting platform for spin torque devices with novel functionalities. In particular, antiferromagnetic spintronics in 2D vdW systems may bring unique advantages in manipulating magnon modes and create new device concepts for microwave electronics.
In this talk, I will first present our recent work in identifying the gigahertz antiferromagnetic resonances within the easy-axis van der Waals (vdW) magnet CrSBr and understanding how their frequencies and intermode coupling can be controlled by the combination of external magnetic fields and magnetic anisotropy [1]. Next, I will show that exchange bias from CrSBr acting on the van der Waals ferromagnet Fe3GeTe2 induces a spatially non-uniform spin configuration through the thickness of the Fe3GeTe2 (FGT) that is not readily achievable with conventional magnetic materials. Furthermore, the in-plane exchange bias provides sufficient symmetry breaking to allow deterministic spin–orbit torque switching of the FGT in CrSBr/FGT/Pt samples at zero applied magnetic field [2].
[1] T. M. J. Cham*, S. Karimeddiny, A. H. Dismukes, X. Roy, D. C. Ralph, and Y. K. Luo*, Anisotropic gigahertz frequency antiferromagnetic resonance in layered van der Waals semiconductor. Nano Letters, 22, 6716-6723 (2022)
[2] T. M. J. Cham*, R. J. Dorrian, X. S. Zhang, A. H. Dismukes, D. G. Chica, X. Roy, A. F. May, D. A. Muller, D. C. Ralph, and Y. K. Luo*, Exchange bias between van der Waals materials: tilted magnetic states and field-free spin-orbit-torque switching. Advanced Materials, 2305739 (2023)
Bio: Kelly is a Gabilan Assistant Professor of Physics and Astronomy at the University of Southern California starting in 2023. She was previously a Presidential Postdoctoral Fellow and Honorary Kavli Fellow at Cornell University studying spin torque dynamics in van der Waals magnets with Dan Ralph (primary), Kin Fai Mak, and Jie Shan. She received her Ph.D. in physics at the Ohio State University studying information transduction between spintronic, photonic, and magnetic states in two-dimensional hybrid systems under the guidance of Roland Kawakami in 2019. She obtained her Bachelor of Science in Physics at the Hong Kong University of Science and Technology.
