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Presentation given by Dr. Yabin Fan from UCLA


Topological Insulator-based Spin-Orbitronics
10:00, Sept. 25th (Friday)
Meeting room, Center of Electron Microscopy
Yabin Fan
Electrical Engineering Department, University of California, Los Angeles
Recent demonstrations of magnetization switching induced by in-plane current in heavy metal/ferromagnetic heterostructures have drawn great interest to spin torques arising from the large spin-orbit coupling (SOC) in various materials. Considering the intrinsic strong SOC, topological insulators (TIs) are expected to be promising candidates for exploring spin-orbit torque (SOT)-related physics. In the first part of the presentation, we will show the magnetization switching through current-induced giant SOT in both TI/Cr-doped TI bilayer [1] and uniformly Cr-doped TI films. In particular, we show that the current-induced SOT has strong correlation with the spin-polarized surface currents in the film. Besides, we will present the second-harmonic methods which are used to measure the spin torque efficiency in these magnetic TI structures. We find that the spin torque efficiency is in general three orders of magnitude larger than those reported in heavy metal/ferromagnetic heterostructures. Moreover, we will discuss the electric-field control of the giant SOT in magnetically doped TIs [2]. In the second part of the presentation, we will introduce the quantum anomalous Hall effect (QAHE) [3] in Cr-doped TI films and explore its correlation with the current-induced SOT. Finally, we will discuss the high temperature applications of the giant SOT in TI-based magnetic structures.
[1] Y. Fan, P. Upadhyaya, X. Kou, M. Lang, S. Takei, Z. Wang, J. Tang, L. He, L.-T. Chang, M. Montazeri, G. Yu, W. Jiang, T. Nie, R. N. Schwartz, Y. Tserkovnyak & K. L. Wang. “Magnetization switching through giant spin–orbit torque in a magnetically doped topological insulator heterostructure”. Nature Mater. 13, 699-704 (2014). doi:10.1038/nmat3973
[2] Y. Fan, X. Kou, P. Upadhyaya, and K. L. Wang. In review (2015).
[3] X. Kou, S.-T. Guo, Y. Fan, L. Pan, M. Lang, Y. Jiang, Q. Shao, T. Nie, K. Murata, J. Tang, Y. Wang, L. He, T.-K. Lee, W.-L. Lee, and K. L. Wang. “Scale-Invariant Quantum Anomalous Hall Effect in Magnetic Topological Insulators
beyond the Two-Dimensional Limit”. Phys. Rev. Lett. 113, 137201 (2014).
Yabin Fan is currently a Ph.D. student in the Device Research Laboratory (DRL) at University of California, Los Angeles (UCLA) under the mentorship of Prof. Kang L. Wang. He received his B.S. degree in physics from Nankai University, China in 2009. In September 2009, he joined the DRL in the Electrical Engineering Department at UCLA to pursue his M.S./Ph.D. degrees. He received the M.S. degree in March 2012 and expects to receive the Ph.D. degree in 2015. He has been a Graduate Student Researcher since 2009. His research focuses on topological insulator-based spin-torque devices, strong spin-orbit coupling magnetic structures and various spin-orbit torque phenomena. He is a member of the American Physical Society (APS). During his graduate studies, he has authored and co-authored 20 journal papers, given 5 conference presentations (including one invited symposium presentation in the 2015 APS March Meeting), and presented 8 posters in conferences and reviews. Besides, he has also received the Outstanding Poster Award in the Functional Accelerated nanoMaterial Engineering (FAME) research center annual review in 2013, the Best Student Presentation Finalist Award in the 59th Magnetism and Magnetic Materials annual conference in 2014 and the Chinese Government Award for outstanding graduate students abroad in 2015, etc.