A joint research team from the National Institute for Materials Science (NIMS), the University of Tokyo, Kyoto Institute of Technology, and Tohoku University has demonstrated the creation of thin films of ruthenium dioxide (RuO2).₂) exhibits a third fundamental class of magnetic behavior, crossmagnetism, which is distinct from ferromagnetism and antiferromagnetism.
Magnetic materials play a central role in modern information technology, especially in memory devices. Traditional ferromagnetic materials allow data to be easily written using external magnetic fields, but they are susceptible to interference from stray magnetic fields and can introduce errors as device density increases. Antiferromagnetic materials are resistant to such disturbances, but they cancel out the spin structure, making the stored information difficult to read electrically.
Alternative magnets offer an alternative. Although they do not have a net magnetization like antiferromagnets, they allow electrical readout of their spin-dependent properties. This combination is gaining attention in applications such as high-speed and high-density memory. However, the experimental results regarding the existence of RuO are₂ The actual magnetic properties exhibited are highly variable due to challenges in producing high-quality samples.
To address this issue, the research team created RuO.₂ A thin film with a single crystal orientation on a sapphire substrate. By carefully choosing the substrate and fine-tuning the growth conditions, the researchers were able to control how the atomic lattice aligns during film formation. This control was essential to obtain consistent and interpretable magnetic behavior.
The research team used X-ray magnetic dichroism to directly determine the spin alignment in the film and confirmed that the magnetic poles cancel each other out. They also observed spin-splitting magnetoresistance, meaning that the electrical resistance depends on the spin orientation. This provided electrical evidence for a spin-split electronic structure and supported the existence of alternating current magnetism.
The relationship between crystal orientation and magnetic behavior can be compared to laying tiles on a floor. Placing the tiles at random angles makes it difficult to recognize the pattern. Arranging them in one direction makes the overall structure clear. Similarly, align the crystal axes of RuO₂ We have made it possible to observe the underlying magnetic properties.
“These results demonstrate that controlling crystal orientation is the key to understanding and exploiting the crossmagnetism of RuO.₂ “This approach allows us to combine theoretical predictions with experimental observations,” said a member of the research team.
The experimental results were consistent with first-principles calculations, increasing the confidence in the interpretation. Taken together, the results identify RuO₂ Thin films as a practical platform to study AC magnetism and assess suitability for device applications.
Looking ahead, the team plans to explore memory devices using RuO₂ Achieves efficient and high-speed information processing using thin films. The synchrotron-based magnetic analysis techniques developed in this study can also be applied to other candidate magnetic materials, supporting broader research in spintronics.
The study was published online in the journal Nature Communications on September 24, 2025.
- Publication details:
title: Evidence for a single mutant of variable magnetic RuO2(101) Thin film
author: Song He, Wen Zhenchao, Jun Okabayashi, Yoshio Miura, Tianyi Ma, Tadakatsu Okubo, Takeshi Seki, Hiroaki Sukegawa, Seiji Mitani
journal: nature communications
Doi: 10.1038/s41467-025-63344-y
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