Electric-field control of spin-orbit torque in magnetically doped topological insulators*

Recent advances of spin-orbit torques (SOTs) generated by topological insulators (TIs) [1-2] have drawn increasing interest to the spin-momentum locking feature of TIs' surface states, which can potentially provide a very efficient means to generate SOTs for spintronic applications. In this 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 [3] In particular, we show that the current-induced SOT has significant contribution from the spin-momentum locked surface states of TIs. We find that the spin torque efficiency is in general three orders of magnitude larger than those reported in heavy metal/ferromagnetic heterostructures. In the second part, we will present the electric-field control of the giant SOT in magnetically doped TIs [3], which suggests promising gate-controlled spin-torque device applications. The giant SOT and efficient current-induced magnetization switching exhibited by the magnetic TIs may lead to innovative spintronic applications such as ultralow power dissipation memory and logic devices. [1] Y. Fan, \textit{et al.}, \textit{Nature Mater. }\textbf{13}, 699-704 (2014). [2] A. R. Mellnik, \textit{et al.}, \textit{Nature} \textbf{511}, 449-451 (2014). [3] Y. Fan, \textit{et al}., \textit{under} \textit{preparation}.