GP-Spin Seminar
Basic Tutorial:

Spin-Orbitronics and Orbitronics

4:30 pm, Thursday, May 30, 2024

Advanced Tutorial:

Combining the best of all worlds:
Altermagnets – a new class of magnets

4:30 pm, Friday, May 31
Professor Dr.

Mathias KLÄUI

Instutute of Physics & Materials Science in Mainz, Johannes Gutenberg Universiy
Venue: Seminar Room, 2nd floor, AIMR Main Building
Katahira Campus, Tohoku University
Katahira Campus North Gate

AIMR Main Building

Contact: GP-Spin Office
spin.all[at]tohoku.ac.jp

Co-hosted by AIMR
1022-795-3657 /3487

Basic Tutorial

Spin-Orbitronics and Orbitronics
M. Kläui1,2*

1

Institute of Physics, Johannes Gutenberg University Mainz, 55099 Mainz, Germany
Center for Quantum Spintronics, Norwegian University of Science and Technology, 7491 Trondheim, Norway*Klaeui@uni-mainz.de2

Novel spintronic devices can play a role in the quest for GreenIT if they are stable and can transport and manipulate
spin with low power. Devices have been proposed, where switching by energy-efficient approaches is used tomanipulate topological spin structures [1,2].
We combine ultimate stability of topological states due to chiral interactions [3,4] with ultra-efficient manipulation
using novel spin torques [3-5]. In particular orbital torques [6] increase the switching efficiency by more than afactor 10 enabling low power memory devices.
We use skyrmion dynamics for non-conventional stochastic computing applications, where we developed
skyrmion reshuffler devices [7] based on skyrmion diffusion, which also reveals the origin of skyrmion pinning[7]. Such diffusion can furthermore be used for Token-based Brownian Computing and Reservoir Computing [8].

References[1] G. Finocchio et al., J. Phys. D: Appl. Phys., vol. 49, no. 42, 423001, 2016.
[2] K. Everschor-Sitte et al., J. Appl. Phys., vol. 124, no. 24, 240901, 2018.
[3] S. Woo et al., Nature Mater., vol. 15, no. 5, pp. 501–506, 2016.
[4] K. Litzius et al., Nature Phys., vol. 13, no. 2, pp. 170–175, 2017.
[5] K. Litzius et al., Nature Electron., vol. 3, no. 1, pp. 30–36, 2020.
[6] S. Ding et al. Phys. Rev. Lett. 125, 177201, 2020; Phys. Rev. Lett. 128, 067201, 2022.
[7] J. Zázvorka et al., Nature Nanotechnol., vol. 14, no. 7, pp. 658–661, 2019;
R. Gruber et al., Nature Commun. vol. 13, pp. 3144, 2022.
[8] K. Raab et al., Nature Commun. vol. 13, pp. 6982, 2022;
M. Brems et al., Appl. Phys. Lett. 119, 132405, 202

Advanced Tutorial
Combining the best of all worlds: Altermagnets – a new class of magnets
M. Kläui1,2*
1

Institute of Physics, Johannes Gutenberg University Mainz, 55099 Mainz, Germany
Center for Quantum Spintronics, Norwegian University of Science and Technology, 7491 Trondheim, Norway*Klaeui@uni-mainz.de2

So far, spintronics has relied on ferromagnetic materials with parallel alignment of spins. However, ferromagnets
exhibit comparatively slow dynamics. Recently antiferromagnets have moved to the forefront of research. While
known for a long time, antiferromagnetically ordered systems have previously been considered, as “interesting butuseless”. However, since antiferromagnets potentially promises faster operation, enhanced stability and higher
integration densities, they could potentially become a game changer for new spintronic devices. Here we show
how antiferromagnets can be used as active spintronics devices by demonstrating the key operations of “reading”[1], “writing” [2], and “transporting information” [3] in antiferromagnets. While possible, it has turned out to bedifficult to read and write antiferromagnets because of the zero spin – polarization due to the antiparallel alignmentof spins and thus zero net moment.
Here we combine the best of (i) ferromagnets: spin-polarized currents and (ii) antiferromagnets: zero net momentwith ultra-fast dynamics in a new class of magnets: ALTERMAGNETS [4].
Going beyond ferromagnets and antiferromagnets, we develop altermagnetic materials [4,5]. This recently
identified class magnets with collinear antiferromagnetic magnetic order can exhibit spin splitting and particularspin transport properties and torques [4]. Here we demonstrate the spin splitting in RuO2 and CrSb [5] und analyze
particular symmetries of the Hall signal in the altermagnet hematite [6].

References[1] S. Bodnar et al., Nature Comm. 9, 348 (2018); S. Bommanaboyena et al., Nature Comm. 12, 6539 (2021).
[2] H. Meer et al., Nano Lett. 21, 114 (2020); S. P. Bommanaboyena et al., Nature Commun. 12, 6539 (2021); C. Schmittet al., Nano Lett. 24, 1471 (2024).
[3] R. Lebrun et al., Nature 561, 222 (2018). R. Lebrun et al., Nature Commun. 11, 6332 (2020). S. Das et al., NatureCommun. 13, 6140 (2022).
[4] L. Smejkal et al., Phys. Rev. X 12, 040501 (2022).
[5] O. Fedchenko et al., Sci. Adv. 10, eadj4883 (2024)); S. Reimers et al., Nature Commun. 15, 2116 (2024)).
[6] E. Galindez-Ruales et al., arxiv:2310.16907