The terminology "altermagnetism" has recently been adopted to describe collinear magnetic order with no net magnetization and non-relativisitic, momentum-dependent spin-splitting. The archetypal material used to theoretically explore altermagnetism is RuO2, but there has been significant debate as to whether RuO2 possesses magnetic, let alone altermagnetic, order. To address questions surrounding the nature of magnetism in RuO2, we combine symmetry-sensitive torque magnetometry and magnetization measurements in single crystals. The data are inconsistent with collinear magnetic order possessing a N\'eel vector along the c−axis. Torque magnetometry further demonstrates an isotropic magnetic susceptibility within the ab−plane, indicative of neither a N\'eel vector within the ab−plane nor a field-induced N\'eel vector reorientation. Magnetic quantum oscillations from both techniques reveal a nearly spherical Fermi surface pocket at the Brillouin zone center, in agreement with paramagnetic electronic structure calculations. Taken together, these data indicate no detectable long-range magnetic order and, by extension, suggest no altermagnetism in high-quality RuO2 single crystals.
@article{arxiv.2504.21138,
title = {Determining the Nature of Magnetism in Altermagnetic Candidate RuO$_2$},
author = {Tiema Qian and Aya Rutherford and Eun Sang Choi and Haidong Zhou and Boris Maiorov and Minseong Lee and Christopher A. Mizzi},
journal= {arXiv preprint arXiv:2504.21138},
year = {2025}
}