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arXiv · 2504.21138

Determining the Nature of Magnetism in Altermagnetic Candidate RuO$_2$

Tiema Qian·Aya Rutherford·Eun Sang Choi·Haidong Zhou·Boris Maiorov·Minseong Lee·Christopher A. Mizzi
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Abstract

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 RuO$_2$, but there has been significant debate as to whether RuO$_2$ possesses magnetic, let alone altermagnetic, order. To address questions surrounding the nature of magnetism in RuO$_2$, 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 RuO$_2$ single crystals.

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Tiema Qian, Aya Rutherford, Eun Sang Choi, Haidong Zhou, Boris Maiorov, Minseong Lee, Christopher A. Mizzi. 2025-04-29. Determining the Nature of Magnetism in Altermagnetic Candidate RuO$_2$. https://arxiv.org/abs/2504.21138

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