December 16, 2025 by National Institute for Materials Science
Collected at: https://phys.org/news/2025-12-altermagnetism-ruo-thin-magnetic-material.html
A research team has demonstrated that thin films of ruthenium dioxide (RuO₂) exhibit altermagnetism—the defining property of what is now recognized as the third fundamental class of magnetic materials.
Altermagnets have the potential to overcome limitations associated with current magnetic random access memory using conventional ferromagnets and are attracting attention as promising materials for next-generation high-speed, high-density memory devices.
In addition to identifying RuO₂ as a strong candidate for such applications, the study also highlights the possibility of enhancing its functionality through control of crystallographic orientation.
The research findings are published in Nature Communications.
The joint research team includes members from NIMS, the University of Tokyo, Kyoto Institute of Technology and Tohoku University.
Altermagnetism and memory devices
Ruthenium dioxide (RuO₂) has been attracting attention as a promising candidate for exhibiting altermagnetism—a proposed third fundamental class of magnetism.
Conventional ferromagnetic materials used in memory devices allow easy data writing via external magnetic fields, but are prone to recording errors caused by stray magnetic fields, which limit further increases in data density.
Antiferromagnetic materials, on the other hand, are robust against such external disturbances. However, because their atomic-level spins cancel each other out, it is difficult to electrically read information from them. This has driven demand for magnetic materials that combine resistance to external disturbances with compatibility with electrical readout, and ideally also allow rewritability.
Experimental challenges and breakthroughs
However, experimental results concerning altermagnetism in RuO₂ have been inconsistent worldwide, hindering a clear understanding of its fundamental nature. Moreover, the lack of high-quality thin-film samples with uniform crystallographic orientation has prevented conclusive experimental verification.
The team successfully fabricated single-orientation (single-variant) RuO2 thin films with aligned crystallographic axes on sapphire substrates. They clarified the mechanism by which crystallographic orientation is determined through optimal substrate selection and fine-tuning of growth conditions.
Using X-ray magnetic linear dichroism, the team identified the spin arrangement and magnetic ordering in which the net magnetization (N–S poles) cancels out. Furthermore, they observed spin-split magnetoresistance—a phenomenon in which electrical resistance varies depending on spin orientation—thereby electrically verifying the spin-splitting electronic structure.
Implications for future memory devices
The results of the X-ray magnetic linear dichroism were consistent with first-principle calculations on the magneto-crystalline anisotropy, demonstrating that the RuO2 thin films exhibit altermagnetism. This finding strongly supports the potential of RuO2 thin films as promising materials for next-generation high-speed, high-density memory devices.
Building on these results, the research team aims to develop next-generation high-speed, high-density magnetic memory devices utilizing RuO₂ thin films. Such devices are expected to contribute to more energy-efficient information processing by leveraging the inherently high-speed and high-density characteristics of altermagnetism.
Furthermore, the synchrotron-based magnetic analysis technique established in this study can be applied to the exploration of other altermagnetic materials and the development of spintronic devices.
More information: Cong He et al, Evidence for single variant in altermagnetic RuO2(101) thin films, Nature Communications (2025). DOI: 10.1038/s41467-025-63344-y
Journal information: Nature Communications
Leave a Reply