Altermagnets are a newly discovered class of magnetic materials [1] that exhibit alternating spin polarization in both their real space and reciprocal space. This intriguing feature allows altermagnetic materials to exhibit magnetic order that is compatible with important spintronic effects like giant magneto resistance [2] and anomalous Hall effect (AHE) [3], which were previously believed to be absent in collinear magnetically compensated systems.
The detection of the anomalous Hall effect in RuO₂ has demonstrated the unconventional breaking of time-reversal symmetry in the electronic structure of altermagnets. Using symmetry analysis and ab initio calculations, we employed a field-induced reorientation of the Néel vector in RuO₂, displacing it from the easy-axis towards the [110] hard-axis to expose the anomalous Hall signal in this altermagnet. Our findings affirm the presence of an anomalous Hall effect in our RuO₂ thin film samples, reporting for the first time saturation above 55 T [4].
Additionally, I will focus on detailed magnetometry measurements on RuO₂ thin films grown on TiO₂ substrates with various orientations and compare the results to show specious effects coming from the substrate.

References:
[1] L. Smejkal, J. Sinova, and T. Jungwirth, Phys. Rev. X, vol. 12, p. 031042, Sep 2022. https://link.aps.org/doi/10.1103/PhysRevX.12.031042
[2] L. Smejkal, A. B. Hellenes, R. Gonzalez-Hernandez, J. Sinova, and T. Jungwirth, Phys. Rev. X, vol. 12, p. 011028, Feb 2022. https://link.aps.org/doi/10.1103/PhysRevX.12.011028
[3] L. Smejkal, R. Gonzalez-Hernandez, T. Jungwirth, and J. Sinova, Science Advances, vol. 6, no. 23, p. eaaz8809, 2020. https://www.science.org/doi/abs/10.1126/sciadv.aaz8809
[4] . Tschirner, P. Keßler, R. D. Gonzalez Betancourt, T. Kotte, D. Kriegner, B. B ̈uchner, J. Dufouleur, M. Kamp, V. Jovic, L. Smejkal, J. Sinova, R. Claessen, T. Jungwirth, S. Moser, H. Reichlova, and L. Veyrat, APL Materials, vol. 11, no. 10, Oct. 2023. http://dx.doi.org/10.1063/5.0160335