After introducing spin, the quantum physical property of electrons, semiconductor devices have become a new type of device with the advantages of high speed, high integration, and low power consumption, that is, spintronic devices, among which the representative one is magnetic random-access memory (MRAM). As one of the methods to break through the bottlenecks of energy efficiency and reliability for traditional charge-mode memories, the development of spintronic devices has received great attention recently. My research focus has been mostly on the mechanism study of charge-spin conversion in different ferromagnetic and antiferromagnetic heterostructures, which falls under the umbrella of electrical engineering and nanotechnology. The main objective of my research is to discover materials with larger charge-spin conversion efficiency so that the power consumption and operation speed of spintronics device.

Traditional magnetoresistive random-access memory (MRAM) devices use spin-transfer torque generated by an external current to write data. However, since the current paths for ‘write’ and ‘read’ operations are shared, this increases the risk of magnetic tunnel junction breakdown, reducing device lifespan and read-write reliability. In contrast, spin-orbit torque (SOT) technology utilizes the spin Hall effect to control magnetization through an in-plane current, effectively resolving the issue of shared read-write channels. Nevertheless, in current SOT-based memory devices, the required current density for switching magnetic states remains relatively high. Therefore, it is necessary to explore material-based approaches to enhance spin-orbit torque efficiency, thereby reducing operating currents and mitigating issues such as device overheating.

(Figure is taken from Wikipedia)

Researchers have recently shown through theoretical predictions that transverse spin currents in various polarization directions can be generated in ferromagnets, but there are very few experimental studies exploring the use of ferromagnetic materials as spin sources. Part of the challenge comes from the difficulty in generating and detecting spin currents in two ferromagnetic layers in close contact due to the strong exchange coupling at the interface. Based on this background, we used the spin current generated in the ferromagnetic layer to drive magnetic switching in the adjecent noncollinear antiferromagnetism, providing direct evidence for the generation of transverse spin currents in ferromagnets. In this study, we innovatively used the ferromagnetic layer as a spin source to achieve controllable manipulation of the antiferromagnetic state and observed field-free switching, indicating that out-of-plane spins can be generated in ferromagnetic materials.


Adv. Mater. 37, 2408340 (2025)
Phys. Rev. Appl. 13, 034072 (2020)

In recent years, researchers have discovered that the spin-orbit moment efficiency of ferromagnetic structures has been significantly improved after combining with oxygen. However, due to the difficulty in determining the location and dosage of oxygen, the relevant mechanism and exact role are still inconclusive. We designed the in-situ study method to investigate the oxygen exposure effect on spin-orbit torque efficiency in Pt/Co bilayers in ultrahigh vacuum system and found that oxygen exposure on ferromagnet can increase the spin-orbit torque efficiency by enhancing the surface Rashba effect. In this study, the oxygen exposure amount and location is precisely controlled that the exact oxygen effect on spin-orbit torque is unveiled. We also continued to explore the effect of oxygen exposure on the current-induced reversal in this bilayer structures, and revealed that oxygen can reduce the critical current not only by enhancing the spin-orbit moment but also by regulating the local anisotropy difference of ferromagnet layer.

We also grew amorphous Weyl semimetal WTe2 by magnetron sputtering, and detected a very high charge-spin conversion efficiency. Unlike the single-crystalline Weyl semimetals prepared by exfoliation method reported previously, the Weyl semimetals grown by vacuum sputtering have the advantages of easy preparation and compatibility with semiconductor industry processes. We realized the control of the state of perpendicular anisotropic film in Weyl semimetal-based structure via external current, These findings show that sputtered Weyl semimetals have the potential to replace traditional heavy metals as spin current sources.


Sci. rep. 9, 17254 (2019)
Appl. Phys. Lett. 116, 122404 (2020)
Appl. Phys. Lett. 118, 042401 (2021)