Transversely-Polarized Spin Current Generation from Ferromagnetic Metals

Xin Fan^1*

¹Physics and Astronomy, University of Denver, Denver, CO, USA

* Presenter:Xin Fan, email:xin.fan@du.edu

The anomalous Hall effect, discovered by Edwin Hall in 1880, describes a phenomenon that an electric current perpendicular to magnetization of a magnetic material can produce a charge accumulation in the direction orthogonal to both electric current and magnetization. Through century-long theoretical and experimental efforts, it is now understood that the anomalous Hall effect arises from the spin-orbit coupling. The understanding of the anomalous Hall effect has also led to the discovery of new spin-orbit effects, such as the spin Hall effect, where an electric current generates spin accumulations in nonmagnetic materials. The spin Hall effect also exists in ferromagnetic materials, in a more complicated and interesting way. There exist a group of spin-orbit effects associated with transverse spins – spins polarized perpendicular to the magnetization, which we refer to this group of spin-orbit effects as transverse-spin-orbit effects in magnetic materials. In my talk, I will present our experimental observations of two unique transverse spin-orbit effects: (1) spin-to-charge interconversion with unconventional spin rotation symmetry and (2) the generation of anomalous spin-orbit torque in a single-layer magnetic film – a hidden counterpart to the anomalous Hall effect. I will also discuss the impact of these effects on the understanding of general spin-charge conversion phenomena.

Reference
[1] Humphries, A. M., Wang, T., et al. Observation of Spin-Orbit Effects with Spin Rotation Symmetry, Nature Communications, 8, 911 (2017)
[2] Aljuaid, W. S., Allen, S. R., Davidson, A., Fan, X., Free-layer-thickness-dependence of the spin galvanic effect with spin rotation symmetry, Applied Physics Letters 113, 122401 (2018)
[3] Wang, W., Wang, T., et al. Anomalous Spin-orbit Torques in Magnetic Single-layer Films, Nature Nanotechnology, 14, 819-824 (2019)
[4] Davidson, A., Amin, V. P., Aljuaid, W. S., Haney, P. M., Fan, X., Perspectives of Electrically Generated Spin Currents in Ferromagnetic Materials, Physics Letters A 126228 (2020)
[5] Greening, R.W. and Fan, X., Influence of nonuniform magnetization reorientation on spin-orbit torque measurements, arXiv: 2207.10349 (2022)

Keywords: Spin Hall, Transverse Spin, Spin Rotation