Theory of spin-orbit torques in metallic bilayers
Mardi 25 juin 2013 11:00
- Duree : 1 heure
Lieu : Salle de Séminaire de SPINTEC, Bât 1005 au 2ème étage, CEA Grenoble, 17 rue des martyrs
Orateur : Aurélien MANCHON (Materials Science and Engineering Dept. of KAUST, Saudi Arabia)
It has been recently demonstrated that appropriately designed spin-orbit coupling (SOC) can be used to generate spin torque (coined as SOC-torque) in a single ferromagnet, without the need of an external polarizer [1-3]. This effect has been observed experimentally in both perpendicular and in-plane magnetic systems, consisting in ferromagnetic metals [4,5] and dilute magnetic semiconductors [6]. Interestingly, due to the complex structure of metallic systems, the microscopic origin of the current-driven magnetization dynamics is still under debate and the contributions of spin Hall and band structure effects are still under intense investigation [7].
In this work, I will address the different origins of the SOC-torque and discuss experimental implications. In a first part, I will introduce a diffusive model for spin Hall effect in metallic bilayers and show how it can generate spin torque, anisotropic magnetoresistance and anomalous Hall effect. The connection between these three effects can be exploited as a probe of the spin Hall origin of the SOC-torque. In a second part, I will address the nature of the band structure of such bilayers in the presence of interfacial symmetry breaking using ab initio calculations. It can be shown such an inversion asymmetry in the system produces two important effects : the well-known Rashba field (and related Rashba torque) on the itinerant electrons, and the celebrated Dzyaloshinskii-Moriya interaction on the localized spins. In a third part, I will discuss the nature of the Rashba torque and its complex angular dependence in a simplified 2-dimensional model. Implications in terms of experimental observations will be proposed.
[1] A. Manchon and S. Zhang, Phys. Rev. B 78, 212405 (2008) ; Phys. Rev. B 79, 094422 (2009).
[2] X. Wang and A. Manchon, Phys. Rev. Lett. 108, 117201 (2012) ; arXiv:1111.5466.
[3] K. Obata, and G. Tatara, Phys Rev. B 77, 214429 (2008).
[4] I. M. Miron et al., Nature Materials 9, 230 (2010) ; U. H. Pi et al., Appl. Phys. Lett. 97, 162507 (2010) ; I. M. Miron, et al. Nature (London) 476, 189 (2011).
[5] L. Liu, et al., Phys. Rev. Lett. 106, 036601 (2011) ; Science 336, 555 (2012).
[6] A. Chernyshov et al., Nature Physics 5, 656 (2009) ; M. Endo, F. Matsukura, and H. Ohno, Appl. Phys. Lett. 97, 222501 (2010) ; Fang et al. Nature Nanotechnology 6, 413 (2011).
[7] P. Haney, K.-J. Lee, H.-W. Lee, A. Manchon and M. D. Stiles, arXiv:1301.4513
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Contact : olivier.boulle@cea.fr
Discipline évènement : (Physique)
Nature évènement : (Séminaire)
Evènement répétitif : (Séminaire nanomagnétisme et électronique de spin)
Site de l'évènement : Site CEA avec accès badge
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