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A research team affiliated with UNIST announced the successful development of a novel semiconductor device that uses a new class of materials, known as altermagnetism. This breakthrough is expected to significantly advance the development of ultra-fast, energy-efficient AI semiconductor chips.
Jointly led by Professor Jung-Woo Yoo from the Department of Materials Science and Engineering and Professor Changhee Sohn from the Department of Physics at UNIST, the team succeeded in fabricating magnetic tunnel junctions (MTJs) using altermagnetic ruthenium oxide (RuO2). They also measured a practical level of tunneling magnetoresistance (TMR) in these devices, demonstrating their potential for spintronic applications.
The research was led by Seunghyun Noh from the Department of Materials Science and Engineering and Kyuhyun Kim from the Department of Physics at UNIST. The findings were published in Physical Review Letters on June 20, 2025.
MTJs are critical components in magnetic random access memory (MRAM) devices. While MRAM offers advantages like non-volatility and low power consumption, its widespread use has been limited by reliance on ferromagnetic materials, which require significant energy for spin reversal, have limited switching speeds, and are sensitive to external magnetic interference.
The researchers developed an altermagnetic material-based device capable of overcoming these limitations. Unlike ferromagnets, altermagnetic materials can store information via electron spin while being less affected by external magnetic fields, enabling ultra-fast switching.
In this study, the team used RuO2, one of the most studied altermagnetic candidates, though its properties have been debated. They synthesized RuO2 thin films with atomic precision under high-vacuum conditions and fabricated MTJs by depositing insulating and ferromagnetic layers sequentially.
When the magnetic orientation of the ferromagnetic layer was changed, a variation in TMR was observed, providing experimental evidence of the device’s potential as a magnetic memory element.
This research marks the first experimental confirmation that TMR varies depending on the spin direction in altermagnetic MTJs, representing a major step toward realizing altermagnetic AI memory semiconductors. The team is now working to enhance the magnitude of TMR effects in future device designs.
Conducted in less than a year and modeled after the US DARPA program, this project aims to rapidly achieve high-impact breakthroughs in fundamental science in Korea.
DongHo Kim of the National Research Foundation of Korea (NRF), overseeing the project, stated, “This achievement reflects the dedication of researchers exploring the largely uncharted field of altermagnetism. We will continue to support this technology, which could be a significant leap forward for the semiconductor industry.”
More information:
Seunghyeon Noh et al, Tunneling Magnetoresistance in Altermagnetic RuO2 -Based Magnetic Tunnel Junctions, Physical Review Letters (2025). DOI: 10.1103/nrk5-5zrj
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Tunneling magnetoresistance in altermagnetic RuO₂-based magnetic tunnel junctions (2025, July 17)
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