‘Tuning’ nonmagnetic material reveals hidden magnetic state

Finding hidden properties could create faster, more energy efficient electronics

MINNEAPOLIS / ST. PAUL (03/06/2026) — Researchers at the University of Minnesota Twin Cities have discovered a new way to turn a common, nonmagnetic material into a high-temperature “altermagnet”—a recently proposed and unusual form of magnetism.

The discovery, published in PNAS, provides a new framework for designing materials for faster and more efficient electronic and spintronic devices. 

Altermagnets combine the best parts of two different types of materials. They have the reliability of the magnets we use today, but don't produce the magnetic interference that usually slows down electronics. Although theoretical work had suggested that the material, RuO₂, might have a magnetic state, experimental evidence had remained difficult to find for years.

To resolve this long-standing question, the team took a different approach. Instead of studying RuO₂ in its natural, relaxed state—or bulk form, they engineered the material as an ultra-thin film and applied epitaxial strain—a technique that gently stretches a crystal at the atomic scale. This precise stretching altered the material’s internal symmetry and revealed a magnetic phase that does not exist in bulk RuO₂.

“RuO₂ is like a slack guitar string that doesn’t produce any sound,” said Bharat Jalan, the Shell Chair Professor in the University of Minnesota Department of Chemical Engineering and Materials Science and senior author on the paper. “By carefully stretching the material, we effectively tuned it until a hidden magnetic state emerged. The key was controlling the material’s structure at the atomic level with extreme precision, ensuring every atom was exactly where it needed to be.”

Using state-of-the-art epitaxial synthesis and advanced laser-based optical probes, the researchers directly observed the transition to an altermagnetic state in films only two nanometers thick—about 50,000 times thinner than a human hair. These tools allowed the team to not only stabilize hidden magnetism but also mapping the electronic and magnetic phase diagram with unprecedented precision. 

In addition to uncovering altermagnetism, the strained RuO₂ films displayed a rare combination of properties. They became polar, metallic and altermagnetic at the same time—a combination which had never been observed in this material. Remarkably, the altermagnetic phase remained stable at temperatures up to 500 Kelvin (440°F), making it promising for real-world applications. 

"This work highlights how advances in synthesis and state-of-the-art optical probes can unlock new physics that was previously hidden," said Seunggyo Jeong, a postdoctoral researcher in the University of Minnesota Department of Chemical Engineering and Materials Science and lead author on the paper. "It suggests that many materials once thought to be nonmagnetic may actually host unexpected quantum states when engineered with sufficient precision."

The research was supported by the Air Force Office of Scientific Research and the U.S. Department of Energy with experiments carried out in part at the University of Minnesota Characterization Facility.

In addition to Jalan and Jeong, the University of Minnesota team included Sreejith Nair, Luca Buiarelli, Turan Birol from the Department of Chemical Engineering and Materials Science along with Rafael M. Fernandes from the School of Physics and Astronomy. This paper was written in collaboration with Gwangju Institute of Science and Technology, McMaster University, Sungkyunkwan University, Massachusetts Institute of Technology, Nagoya University, University of Kentucky, University of Illinois Urbana-Champaign and University of Michigan. 

Read the full paper entitled, “Altermagnetic Polar Metallic phase in Ultra-Thin Epitaxially Strained RuO₂ Films,” on the PNAS website.

Story by Kalie Pluchel