Giant Orbital Hall Effect and Orbital-to-Spin Conversion in 3d, 5d and 4f Metallic Heterostructures

Recent theories have shown that an electric field can induce a transverse flow of orbital angular momenta in elemental metals, even if crystal field and band structure effects completely quench the orbital magnetism at equilibrium [1-3]. In particular, electric currents in 3d elements can generate a substantial non-equilibrium orbital accumulation that is comparable to or even larger than the spin accumulation caused by the spin Hall effect and the Rashba-Edelstein effect in the 5d elements [4,5]. The generation of orbital currents plays a pivotal role in inducing spin-orbit torques in ferromagnets [6-9], which opens new avenues for the realization of spintronic devices for memory and logic applications [10]. In this talk I will discuss the emergence of strong orbital Hall in 3d metals, focusing on the crucial role of orbital-to-spin conversion in the generation of spin-orbit torques [9] and orbital magnetoresistance [11,12]. I will further show how the inclusion of rare-earths as spacer layers or as alloyed species can be used to boost the orbital-to-spin conversion and the torque efficiency in magnetic heterostructures and discuss recent results involving the orbital Rashba-Edelstein effect.



References

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[6] D. Lee et al., Nat. Comm. 12, 6710 (2021).

[7] J. Kim et al., Phys. Rev. B 103, L020407 (2021).

[8] S. Ding et al., Phys. Rev. Lett. 128 (2022) 067201.

[9] G. Sala and P. Gambardella, Phys. Rev. Res. 4 033037 (2022).

[10] A Manchon et al., Rev. Mod. Phys. 91, 035004 (2019).

[11] S. Ding et al., Phys. Rev. Res. 4, L032041 (2022).

[12] G. Sala et al., Phys. Rev. Lett. 131, 156703 (2023).