Abstract
A research team, affiliated with UNIST has made a groundbreaking advancement in controlling spin-based signals within a new magnetic material, paving the way for next-generation electronic devices. Their work demonstrates a method to reversibly switch the direction of spin-to-charge conversion, a key step toward ultra-fast, energy-efficient spintronic semiconductors that do not require complex setups or strong magnetic fields.
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 has experimentally shown that within the altermagnetic material ruthenium oxide (RuO₂), the process of converting spin currents into electrical signals can be precisely controlled and flipped at will. This breakthrough is expected to accelerate the development of low-power devices, capable of processing information more efficiently than current technologies.
RuO₂ has attracted attention as a "third kind" of magnetic material-called an altermagnet-that combines desirable properties of both ferromagnets and antiferromagnets. Theoretically, this material offers the potential to surpass the speed limits of traditional semiconductors and improve energy efficiency. Yet, a major obstacle has been reliably controlling the spin-to-charge conversion process, which is essential for integrating these materials into electronic components.
The team succeeded in demonstrating that by adjusting the internal magnetic order of the material-specifically, the Néel vector-they could reversibly switch the polarity of the spin-to-charge conversion signal. In simple terms, rotating the magnetic orientation within the material by 180 degrees allows the electrical output to switch between positive and negative states. This non-volatile control means information can be stored and manipulated without continuous power, which is crucial for future memory and logic devices.
Unlike previous approaches that relied on complex multilayer structures or external magnetic fields, the researchers built a device by stacking titanium dioxide (TiO₂) substrates with layers of RuO₂ and cobalt-iron-boron (CoFeB). They then used temperature gradients to generate spin currents, which are converted into measurable electrical signals within the RuO₂ layer.
"Our experiments confirm that spin signals in altermagnetic materials like RuO₂ can be reliably controlled and reversed," said Professor Yoo. "This principle could lead to faster, more energy-efficient spin-based logic and memory devices."
Supported by the Ministry of Science and ICT (MSIT) since September 2024, this research highlights Korea's commitment to pioneering advanced scientific breakthroughs. The project aimed to push forward high-impact fundamental research that is often considered too challenging or risky. Impressively, the team completed the entire process-from material synthesis to device testing-in just over a year.
Dongho Kim, Program Manager at the Advanced Science & Technology Research Agency (ASTRA), commented, "This achievement exemplifies innovative research driven by bold experimentation. We will continue supporting such efforts to ensure this technology becomes a key asset for Korea's semiconductor industry."
The study was led by first authors Hyeonjung Jung, now a postdoctoral researcher at GIST, and Gimok So from the Department of Physics at UNIST. Their findings have been published in Nano Letters on November 25, 2025.
Journal Reference
Hyeonjung Jung, Gimok So, Seunghyeon Noh, et al., "Reversible Spin Splitting Effect in Altermagnetic RuO2 Thin Films," Nano Letters, (2025).
