Spin-Orbit Coupling Driven Magnetic Response in Altermagnetic RuO2

The recent prediction of the new magnetic class, altermagnetism, has drawn considerable interest, fueled by its potential to host novel phenomena and to be utilized in next-generation spintronics devices. Among many promising candidates, rutile RuO₂ is a prototypical candidate for realizing the prospects of altermagnetism. However, the experimental studies on RuO₂ are still in the early stages. In this study, the magnetic responses in RuO₂ film are investigated by the Planar Hall effect (PHE). By rotating the external field (H_ext), the PHE exhibits twofold behaviors. Moreover, the planar Hall conductivity shows a nonlinear response to the H_ext. These observed features in PHE resemble those in ferromagnet and topologically nontrivial systems, suggesting the field-induced magnetic response in rutile antiferromagnet. The work provides a strategy for detecting intriguing magnetic responses in altermagnetic materials, promoting further research in altermagnet-based spintronics and novel phenomena.