The TRR 227 kindly invites you to the following Colloquium.

Speaker: Prof. Dr. Xin Fan,
Department of Physics and Astronomy, University of Denver, USA

Title: Transversely-polarized spin current generation from ferromagnetic metals

Abstract:

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.

References

[1]  A. M. Humphries, et al. "Observation of spin-orbit effects with spin rotation symmetry", Nat. Commun. 8, 911 (2017).

[2]   W. S. Aljuaid, S. R. Allen, A. Davidson, and X. Fan, "Free-layer-thickness-dependence of the spin galvanic effect with spin rotation symmetry", Appl. Phys. Lett. 113, 122401 (2018).

[3]  W. Wang, et al. "Anomalous spin-orbit torques in magnetic single-layer films", Nat. Nanotechnol. 14, 819 (2019).

[4]  A. Davidson, V. P. Amin, W. S.  Aljuaid, P. M. Haney, and X. Fan, "Perspectives of electrically generated spin currents in ferromagnetic materials", Phys. Lett. A 384, 126228 (2020).

[5] R. W. Greening and X. Fan, "Influence of nonuniform magnetization reorientation on spin-orbit torque measurements", arXiv: 2207.10349 (2022).