Speaker: Xiaoyu Che
Affiliation: Ph.D. Candidate
Abstract: Spin-orbit torque (SOT) originating from relativistic spin-orbit interaction can switch the direction of adjacent magnetization. Such current-driven switching holds promise for miniaturized magnetic memory devices with high speed, low power consumption, and non-volatility. One of the promising material candidates is topological insulator (TI), which is a novel quantum state of matter with spin-polarized surface states that can drive giant SOT on neighboring magnetization. However, there have been large discrepancies in the reported values of SOT in TIs. Besides, the magnetization switching by TIs requires the assistance of an external magnetic field, which is not practical in applications.
Here, we systematically determine the SOT in magnetically doped TI thin films via both transport and optic approaches. Large SOT generated by the TI with consistent results is observed. Moreover, the experimental results reveal a strong dependence of SOT on temperature and surface state carrier concentration, which could account for the large discrepancies in the reported SOT values and suggest the unique role of surface states. We also demonstrate the realization of field-free magnetization switching in a TI/antiferromagnetic material heterostructure. Accomplished by symmetry breaking with exchange-bias, the field-free switching can be driven by pulsed current with ultra-low current density. Our study takes a step further in utilizing TI to implement more practical and energy-efficient spin-orbit torque magnetic random-access memory (SOT-MRAM).
Biography: Xiaoyu Che received his dual B.S. degree in Electrical Engineering from Iowa State University (summa cum laude) and University of Electronic Science and Technology of China in 2014. He received the M.S. degree in Electrical Engineering from the University of California, Los Angeles, where he is currently pursuing his Ph.D. degree. His research interests focus on spin-orbit torque and novel quantum phenomena in topological matters.
Date(s) - Mar 18, 2020
3:00 pm - 5:00 pm
E-IV Maxwell Room #57-124
420 Westwood Plaza - 5th Flr. , Los Angeles CA 90095