image: Spins accumulate at both edges of the sample owing to the spin Hall effect. Although spin current is expected to flow inside the sample, it has not been observed yet.
Credit: Atsuo Shitade
Osaka, Japan – Researchers from SANKEN (The Institute of Scientific and Industrial Research) at The University of Osaka have developed a new program, “postw90-spin,” that enables high-precision calculations of a novel performance indicator for the spin Hall effect, a phenomenon crucial for developing energy-efficient and high-speed next-generation magnetic memory devices. This breakthrough addresses a long-standing challenge in spintronics research by providing a definitive measure of the spin Hall effect, overcoming ambiguities associated with traditional metrics.
The spin Hall effect, where many researchers recognize an electric field generates a perpendicular spin current, is key to spintronic devices. Previously, the spin Hall conductivity was used as a performance indicator. However, this metric is affected by how the spin current is defined, leading to inconsistencies.
The new program calculates the spin accumulation coefficient, which quantifies the spin accumulation at the edges of a material due to the spin Hall effect. This coefficient is directly measurable and unaffected by ambiguities in defining spin current, offering a more reliable performance prediction for spintronic materials. The program uses first-principles calculations, relying on fundamental quantum mechanics, allowing accurate predictions for real materials.
This advancement is significant for developing next-generation magnetic memory devices. Identifying materials with large spin Hall effects is crucial for creating energy-saving, high-speed, and durable non-volatile memory. By accurately calculating the spin accumulation coefficient, researchers can now effectively screen and identify promising materials for these applications, accelerating the development of advanced spintronic technologies.
"The ambiguity in defining spin current has been a problem that researchers in the field of the spin Hall effect have been aware of, but have turned a blind eye to because other methods are difficult," says Dr. Atsuo Shitade, the lead researcher. "We believe that providing a definite answer to this problem and establishing a method for predicting real materials will greatly advance the microscopic understanding of the spin Hall effect and serve as a bridge between spintronics experiments and theory.”
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The article, “Wannier interpolation of spin accumulation coefficient,” was published in npj Spintronics at DOI: https://doi.org/10.1038/s44306-025-00096-x.
About The University of Osaka
The University of Osaka was founded in 1931 as one of the seven imperial universities of Japan and is now one of Japan's leading comprehensive universities with a broad disciplinary spectrum. This strength is coupled with a singular drive for innovation that extends throughout the scientific process, from fundamental research to the creation of applied technology with positive economic impacts. Its commitment to innovation has been recognized in Japan and around the world. Now, The University of Osaka is leveraging its role as a Designated National University Corporation selected by the Ministry of Education, Culture, Sports, Science and Technology to contribute to innovation for human welfare, sustainable development of society, and social transformation.
Website: https://resou.osaka-u.ac.jp/en
Journal
npj Spintronics
Method of Research
Computational simulation/modeling
Subject of Research
Not applicable
Article Title
Wannier interpolation of spin accumulation coefficient
Article Publication Date
10-Jul-2025