Spin Hall Magnetoresistance at the Altermagnetic Insulator/Pt Interface

by Miina Leiviskä (Czech Academy of Sciences (FZU))

Thursday 21 May 2026, 10:00 → 11:00 Europe/Zurich

OVGA/200

M. Leiviskä¹, R. Firouzmandi², K. Ahn¹, P. Kubaščik³, Z. Soban¹, S. Bommanaboyena¹,
C. Müller¹, D. Kriegner¹, D. Reustlen⁴, S. Sailler⁴, M. Lammel⁴, K. Bestha^2,5, M. Hyvl¹, L. Šmejkal^6,7,1, J. Zelezny¹, A. U. B. Wolter², M. Scheufele^8,9, J. Fischer¹⁰, M. Opel⁸,
S. Geprägs⁸, M. Althammer⁸,  B. Büchner^2,11,12, T. Jungwirth^1,13, L. Nádvorník³,
S. T. B. Goennenwein⁴, V. Kocsis², and H. Reichlova¹

¹Institute of Physics, Czech Academy of Sciences, Czechia

²Institut für Festkörperforschung, Leibniz IFW Dresden, Germany

³Faculty of Mathematics and Physics, Charles University, Czechia

⁴Department of Physics, University of Konstanz, Germany

⁵Institute of Solid State and Materials Physics, TU Dresden, Germany

⁶Max Planck Institute for the Physics of Complex Systems, Germany

⁷Max Planck Institute for Chemical Physics of Solids, Germany

⁸Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, Germany

⁹Technical University of Munich, TUM School of Natural Sciences, Germany

¹⁰Universite Grenoble Alpes, CEA, CNRS, Spintec, France

¹¹Institute of Solid State and Materials Physics and Würzburg-Dresden Cluster of Excellence ct.qmat, Technische Universität Dresden, Germany

¹²Center for Transport and Devices, Technische Universität Dresden, Germany

¹³School of Physics and Astronomy, University of Nottingham, UK

 

Spin Hall magnetoresistance (SMR) is a magnetoresistive effect present in bilayers comprising of a magnet (here insulating) and a heavy metal [1]. It relies on the concerted action of spin Hall effect, inverse spin Hall effect, and dissipation of spin accumulation at the interface. The dissipation of the spin accumulation occurs via various channels, including spin-transfer torque and magnon-mediated spin current transfer. Altermagnets are a new class of collinear compensated magnets with a unique anisotropic spin ordering with characteristic spin-degenerate nodes and alternating even-parity spin polarization that breaks the time-reversal symmetry [2]. In this work, we present a set of SMR measurements in heterostructures of Pt and an insulating and ferroelectric altermagnet candidates Ba₂CoGe₂O₇ [3] and Sr₂CoSi₂O₇. We will first detail the fabrication of devices for SMR experiments on bulk crystals and then discuss characteristic SMR features of the systems under study. We show that in both systems the SMR ratio is unexpectedly large and shows anisotropy depending on in which crystal direction the current is applied. We systematically rule out device-to-device variations, magnetic domains, and magnetocrystalline anisotropy as the main origin of this current-direction anisotropy of the SMR ratio, and also address the possible effects of ferroelectric polarization on the SMR. Finally, we will suggest mechanisms through which the crystal symmetries that characterize the altermagnetic phase of Ba₂CoGe₂O₇ and Sr₂CoSi₂O₇ could give rise to the observed anisotropy.

 

References

[1] H. Nakayama, M. Althammer, Y.-T. Chen, et al. Phys. Rev. Lett. 110, 206601 (2013).

[2] L. Šmejkal, J. Sinova, and T. Jungwirth. Phys. Rev. X 12, 031042 (2022).

[3] M. Leiviskä, R. Firouzmandi, K. Ahn et al. Phys. Rev. Mat. 9, 084403 (2025)