Spin-Orbit Technologies: From Magnetic Memory to Terahertz Generation

Spintronic devices utilize an electric current to alter the state of a magnetic material and thus find great applications 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). I will introduce the basic concepts of SOTs [1,2], and discuss the latest trends in SOT research, such as the exploration of novel material systems like topological insulators and two-dimensional materials to improve the operation efficiency [2,3]. Following this, some of the technical challenges in SOT-based magnetic memory will be highlighted [3]. I will also 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 topological materials [6]. 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. [1] X. Qiu et al., “Characterization and manipulation of spin orbit torque in magnetic heterostructures,” Adv. Mater., 30, 1705699 (2018). [2] Y. Wang et al., “FMR-related phenomena in spintronic devices” J. Phys. D: Appl. Phys., 51, 273002 (2018).[3] R. Ramaswamy et al., “Recent advances in spin-orbit torques: Moving towards device applications” Appl. Phys. Rev., 5, 031107 (2018). [4] Y. Wu et al., “High-performance THz emitters based on ferromagnetic/nonmagnetic heterostructures” Adv. Mater., 29, 1603031 (2017). [5] M. Chen, et al., “Terahertz emission from compensated magnetic heterostructures,” Adv. Opt. Mater., 6, 1800430 (2018).[6] X. Wang, et al., “Ultrafast spin-to-charge conversion at the surface of topological insulator thin films” Adv. Mater. 30, 1802356 (2018).