Antiferromagnetic spintronics

Antiferromagnetic spintronics

Details


Spin transport in collinear antiferromagnets

The recently invigorated field of antiferromagnetic spintronics focuses on the mutual dependence of electron transport and magnetization dynamics in antiferromagnets, which admits vanishing magnetization and where the magnetic ordering is characterized by the staggered magnetic field. We recently published an overview of the potential of such a field in Review of Modern Physics [1], while a series of reviews is in preparation for Nature Physics [1’]. 

Our research showed that in antiferromagnetic spin-valves, spin transfer torque is highly sensitive to disorder [2], which prevents its experimental observation. To solve this issue, we proposed to use either a tunnel barrier as a spacer [3] or a local spin torque using spin-orbit coupling [4,5,6]. In both cases, we demonstrated that the torque is much more robust against impurities, which opens appealing venues for its experimental observation. Finally, we also developed a drift-diffusion theory for collinear antiferromagnets and demonstrated the existence of spin Hall magnetoresistance [7,8]. 

All these results are really thrilling, especially considering the recent experimental breakthroughs (e.g., the electrical manipulation of antiferromagnetic order parameter in CuMnAs by Wadley et al., Science 352, 587 (2016)). We are now interested in even more fascinating systems including antiferromagnetic skyrmions, frustrated magnets and non-collinear antiferromagnets (see left).
                                                    
In antiferromagnetic spin-valve, the spin torque vanishes upon disorder, in sharp contrast to spin torque in ferromagnetic spin-valves (red dots) – From [2].


Spin transport in non-collinear antiferromagnets

Non-collinear antiferromagnets have recently received significant attention with the prediction and experimental observation of anomalous Hall effect in Mn3X (X = Ga, Ge, Sn, Rh, Ir, Pt) compounds. In these materials, the anomalous transport is promoted by the coexistence of both non-collinear magnetic order and spin-orbit coupling (see e.g., Nakatsuji et al., Nature 527, 212 (2015)). 
Building a minimal tight-binding model and exploiting Kubo formula, we investigate the transport and optical properties of an antiferromagnet with non-trivial magnetic configuration in the absence of spin-orbit coupling. Our research showed that the non-trivial magnetic texture leads to topological anomalous Hall effect and spin Hall effect, as well as topological torques and damping enabling the electrical manipulation of the structure. We also show that in spite of the absence of spin-orbit coupling, this class of materials is optically active (unpublished).

Future directions cover the spin relaxation mechanisms, current-driven excitations and magnon propagations in such exciting materials.
                                                                     
Schematics of a 3Q non-collinear antiferromagnet. The special magnetic configuration produces a non-vanishing Berry flux at the level of the unit cell.


Group members involved
Fengjun Zhuo, Papa Birame Ndiaye​ (recently graduated)

Collaborators

​Gilles Gaudin, Vincent Baltz & Mihai Miron, CEA/CNRS/Grenoble Alpes/INP SPINTEC, France
Maxim Tsoi, UT Austin, TX, US

Publications

​[1] Antiferromagnetic spintronics, V. Baltz, A. Manchon, M. Tsoi, T. Moriyama, T. Ono, and Y. Tserkovnyak, Review of Modern Physics (2017).
[1’] Focused issue on antiferromagnetic spintronics: An overview (Part of a collection of reviews on antiferromagnetic spintronics), T. Jungwirth, J. Sinova, A. Manchon, X. Marti, J. Wunderlich, C. Felser, arXiv:1705.10489
[2] Spin transfer torque in antiferromagnetic spin-valves: From clean to disordered regimes, H. Ben Mohamed Saidaoui, A. Manchon, and X. Waintal, Phys. Rev. B 89, 174430 (2014).
[3] Robust spin transfer torque in antiferromagnetic tunnel junctions, H. B. M. Saidaoui, X. Waintal, and A. Manchon, Phys. Rev. B 95, 134424 (2017).
[4] Relativistic Néel-Order Fields Induced by Electrical Current in Antiferromagnets, J. Železný, H. Gao, K. Výborný, J. Zemen, J. Mašek, A. Manchon, J. Wunderlich, J. Sinova, and T. Jungwirth, Phys. Rev. Lett. 113, 157201  (2014).
[5] Spin orbit torque in disordered antiferromagnets, H. B. M. Saidaoui, and A. Manchon, arXiv:1606.04261v1
[6] Spin-orbit torques in locally and globally non-centrosymmetric crystals: Antiferromagnets and ferromagnets, J. Zelezny, H. Gao, A. Manchon, F. Freimuth, Y. Mokrousov, J. Zemen, J. Masek, J. Sinova, and T. Jungwirth, Phys. Rev. B 95, 014403 (2017).
[7] Spin diffusion and torques in disordered antiferromagnets, A. Manchon, (Special Issue: Emerging Leaders), J. Phys. Condens. Matter. 29, 104002 (2017). 
[8] Spin Hall magnetoresistance in antiferromagnet/normal metal bilayers, A. Manchon, Physica Status Solidi (Rapid Research Letters); DOI 10.1002/pssr.201600409 (2017).