Ultra-Thin RuO2 Offers Major Advancements in Spintronics

Researchers at the University of Minnesota Twin Cities have discovered unexpected magnetic behavior in ultra-thin layers of metallic oxide. This finding could accelerate advances in spintronic and quantum computing technologies.

Bharat Jalan and his research group discovered a surprising magnetic behavior in a thin metallic oxide material using an advanced materials growth technique that the group created. Image Credit: University of Minnesota

Published in the Proceedings of the National Academy of Sciences of the United States of America (PNAS), scientists used a sophisticated material growth process called hybrid molecular beam epitaxy to generate ultra-thin layers of RuO₂.

RuO₂ is renowned for its metallic but nonmagnetic properties. However, the team were able to produce magnetic characteristics in the material by applying epitaxial strain to these atomically thin layers. This process is analogous to stretching or compressing a rubber band. 

Our work shows that RuO₂ is not just metallic at the atomic scale, it is the most metallic material we have observed in any oxide, rivaling even elemental metals and 2D materials, second only to graphene. What is more exciting is that this is one of the first experimental demonstrations of an altermagnetic state in ultra-thin RuO₂, a new and exciting class of magnetic material.

Bharat Jalan, Study Senior Author and Professor, Department of Chemical Engineering and Materials Science, University of Minnesota

One key magnetic effect observed in the study was the anomalous Hall effect. This occurs when an electrical current bends in the presence of a magnetic field and is a critical characteristic for next-generation memory and data storage systems.

This effect is usually difficult to generate in metallic RuO₂ and needs strong magnetic fields, but in the ultra-thin RuO₂ produced in this study, the electrical effect was seen and with significantly weaker magnetic fields.

It is exciting because this is not just a laboratory curiosity, we are looking at a material that can be integrated into real devices. This could have major implications for developing smaller, faster, and more energy-efficient technologies, directly relevant to artificial intelligence.

Seunnggyo Jeong, Study First Author and Postdoctoral Researcher, Department of Chemical Engineering and Materials Science, University of Minnesota

The researchers saw magnetic effects even in films that were only two unit cells thick—less than a billionth of a meter. And, in spite of its thinness, the material showed significant metallic content and structural integrity. 

This discovery shows how we can unlock completely new behaviors in materials just by controlling them at the atomic scale. Our calculations confirmed that strain changes the internal structure of RuO₂ in just the right way to make this altermagnetic behavior possible.

Tony Low, Study Co-Author and Professor, Department of Electrical and Computer Engineering, University of Minnesota

The researchers intend to continue investigating how strain and layering might be utilized to manufacture novel material properties. Their goal is to create platform materials for future applications in quantum computing, spintronics, and low-power devices.

Journal Reference:

Jeong, S. G., et al. (2025) Metallicity and anomalous Hall effect in epitaxially strained, atomically thin RuO₂ films. PNAS. doi.org/10.1073/pnas.2500831122.