Exploring Electronic Functionalities of Magnetic Topological Materials for Emerging Memory and Sensing Devices

Tomoya Higo^1,2,3*

¹Department of Electronics and Electrical Engineering, Keio University, Yokohama, Kanagawa, Japan
²Department of Physics, The University of Tokyo, Bunkyo-ku, Tokyo, Japan
³PRESTO, Japan Science and Technology Agency, Kawaguchi, Saitama, Japan

* Presenter:Tomoya Higo, email:higo@elec.keio.ac.jp

Recent discoveries of materials with nontrivial topological band structures, known as topological materials, have drawn attention for their exotic quantum phenomena. They offer unique features, including large transverse responses and high carrier mobility, beyond those of conventional materials [1]. Among them, topological magnets, which couple magnetism with band topology, enable control of Berry curvature and emergent electromagnetic effects via magnetic order, making them promising candidates for next-generation electronics [2].

A key feature of topological magnets is that the emergent field in momentum space does not need to scale with net magnetization in real space. This decoupling allows large electrical responses even in nearly compensated systems, enabling the functionalization of antiferromagnets (AFMs) for ultrafast and low-power data processing. One representative example is the topological AFM Mn₃Sn [3], which has demonstrated room-temperature anomalous Hall and magneto-optical effects—important advances for antiferromagnetic spintronics [4]. Thin-film devices of Mn₃Sn have achieved, for the first time in AFMs, key memory functions such as spin–orbit torque induced perpendicular switching and tunnel magnetoresistance [5], establishing it as one of the model systems for functional AFMs.

These concepts also extend to ferromagnets (FMs). The anomalous Nernst effect (ANE), which is a transverse thermoelectric effect, has been enhanced by nearly an order of magnitude over conventional FMs at room temperature [6]. Its lateral geometry suits thin-film processing, enabling flexible, large-area, and low-cost devices such as heat flux sensors. Thin films of the topological FMs such as Co₂MnGa and Fe₃(Ga, Al, Sn) exhibit large ANE at room temperature and zero field [7], and their compatibility with scalable methods such as roll-to-roll sputtering on flexible PET films supports industrial translation [8].

This work was primarily carried out in collaboration with Prof. S. Nakatsuji’s group at the University of Tokyo, and in close cooperation with Professors S. Miwa, K. Kondou, T. Nomoto, R. Arita, Y. Otani, and many other colleagues.

[1] Hasan & Kane, RMP 82, 3045 (2010); Armitage et al., RMP 90, 015001 (2018).
[2] Nakatsuji & Arita, Annu. Rev. Condens. Matter Phys. 13, 119 (2022); Bernevig et al., Nature 603, 41 (2022).
[3] Nakatsuji, Kiyohara & TH, Nature 527, 212 (2015); Kuroda, Tomita et al., Nat. Matter. 16, 1090 (2017); TH et al., Nat. Photon. 12, 73 (2018).
[4] Jungwirth et al., Nat. Nano. 11, 231 (2016); Šmejkal et al., PRX 12, 040501 (2022).
[5] TH, Kondou et al., Nature 607, 474 (2022); Chen, TH, Tanaka et al., Nature 613, 490 (2023).
[6] Sakai et al., Nat. Phys. 14, 1119 (2019). [7] Sakai,.., TH et al., Nature 581, 53 (2020).
[8] Tanaka, TH et al., Adv. Matter. 35, 2303416 (2023).

Keywords: Topological materials, Antiferromagnetic spintronics, Magneto-thermoelectrics, Non-collinear antiferromagnets/Altermagnets