1月7日 美国康奈尔大学Dr. Shengwei Jiang学术报告:Electrical Control of Magnetism in Atomically Thin Magnets


报告题目:Electrical Control of Magnetism in Atomically Thin Magnets
报告人:Dr. Shengwei Jiang
Cornell University
时间:2019年1月7日 星期一上午 10:00
地点:唐仲英楼 A213

Electrical Control of Magnetism in Atomically Thin Magnets
Shengwei Jiang
School of Applied and Engineering Physics, Cornell University, Ithaca, NY, USA
Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, NY, USA

Controlling magnetism by purely electrical means is a key challenge to fast and energy efficient spintronics devices. Electrical control of magnetism has been explored in a variety of materials including dilute magnetic semiconductors, ferromagnetic metal thin films, magneto-electrics and multiferroics, but remains a formidable challenge. The recent discovery of two-dimensional van der Waals magnets [1-2] has opened a new door for electrical control of magnetism at the nanometer scale through the van der Waals heterostructure device platform.
In this talk, I will discuss our recent observations on electrical control of magnetism in 2D magnet CrI3, and how to utilize it to build a new prototype of spin transistor. In particular, in bilayer CrI3, we observed large linear magnetoelectric effect, whose sign and magnitude are solely determined by its spin symmetry [3]. We also demonstrated doping can drastically change the interlayer spin order, causing AFM-FM phase transition [4]. This electrical-tunable magnetic phase transition enables robust and reversible switching of magnetization in bilayer CrI3 by small gate voltages. With the above findings, we have built a new prototype of spin transistor: a spin tunneling field-effect transistors (Spin-TFET) based on dual-gated graphene/CrI3/graphene heterostructure. These devices show an ambipolar behavior and tunnel conductance that is dependent on the magnetic order in the CrI3 tunnel barrier. The gate voltage switches the tunnel barrier between an interlayer antiferromagnetic and ferromagnetic state under a constant bias magnetic field, thus effectively altering the device between a low and a high conductance state with a large hysteresis. We have achieved electrical write & read of spin configurations in a single device, with a large spin dependent on/off ratio of ~400% [5].

References:
[1] Huang, B. et al. Nature 546, 270 (2017).
[2] Gong, C. et al. Nature 546, 265 (2017).
[3] Jiang, S., Shan, J. & Mak, K.F. Nature Materials 17, 406 (2018).
[4] Jiang, S., Li, L., Wang, Z., Mak, K.F. & Shan, J. Nature Nanotechnology 13, 549 (2018).
[5] Jiang, S., Li, L., Wang, Z., Mak, K.F. & Shan, J. arxiv: 1807.04898

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