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Spintronic devices utilize an electric current to alter the state of a magnetic material and thus
find great application in magnetic memory. Over the last decade, spintronic research has
focused largely on techniques based on spin-orbit coupling, such as spin-orbit torques (SOTs),
to alter the magnetic state. The phenomenon of spin-orbit coupling in magnetic hetero
structures was also recently used to generate terahertz emission and thus bridge the gap
between spintronics and optoelectronics research. I will introduce the basic concepts of SOTs,
such as their physical origin, the effect of SOTs on a magnetic material, and how to
quantitatively measure this effect [1], [2]. Next, I will discuss the latest trends in SOT research,
such as the exploration of novel material systems like topological insulators and twodimensional
materials to improve operation efficiency [3]. Following this, some of the technical
challenges in SOT-based magnetic memory will be highlighted. Moving forward, I will introduce
the process of terahertz generation in magnetic heterostructures [4], where the spin-orbit
coupling phenomenon plays a dominant role. I will discuss the details of how this terahertz
emission process can be extended to novel material systems such as ferrimagnets [5] and twodimensional
materials. The final section will focus on how the terahertz generation process can
be used to measure SOTs in magnetic heterostructures, thus highlighting the interrelation
between terahertz generation and the SOTs, which are linked by the underlying spin-orbit
coupling.
[1] X. Qiu, Z. Shi, W. Fan, S. Zhou, and H. Yang, “Characterization and manipulation of spin orbit
torque in magnetic hetero structures,” Adv. Mater., vol. 30, 1705699, Apr. 2018.
[2] Y. Wang, R. Ramaswamy, and H. Yang, “FMR-related phenomena in spintronic devices” J. Phys.
D: Appl. Phys., vol. 51, 273002, Jun. 2018.
[3] R. Ramaswamy, J. M. Lee, K. Cai, and H. Yang, “Recent advances in spin-orbit torques: Moving
towards device applications” Appl. Phys. Rev., vol. 5, 031107, Sep. 2018.
[4] Y. Wu, M. Elyasi, X. Qiu, M. Chen, Y. Liu, L. Ke, and H. Yang, “High-performance THz emitters
based on ferromagnetic/nonmagnetic hetero structures” Adv. Mater., vol. 29, 1603031, Jan. 2017.
[5] M. Chen, R. Mishra, Y. Wu, K. Lee, and H. Yang, “Terahertz emission from compensated magnetic
heterostructures,” Adv. Opt. Mater., vol. 6, 1800430, Sep. 2018.