Predicting spin accumulation for faster, greener memory

Researchers from the University of Osaka have developed a program, ‘postw90-spin’, that enables high-precision calculations of a novel performance indicator for the spin Hall effect, a phenomenon crucial for developing high-speed, next-generation magnetic memory devices. This research development addresses a longstanding 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 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 designed, leading to inconsistences.

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 could help develop 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 screen and identify promising materials for these applications, thereby 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. 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,” said Dr Atsuo Shitade, the lead researcher.

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