A joint research group led by Professors Masaaki Tanaka and Shinobu Oya, together with Nippon Telegraph and Telephone (NTT) and others, has succeeded in reversing the direction of magnetization of a thin film of a special magnet called SrRuO₃ (hereafter SRO), a Weyl semimetal, simply by applying a current to it. To obtain the spin-orbit torque (SOT), the rotational force acting on the magnetization from the current, a bilayer consisting of a thin film of the magnet and an expensive heavy metal film has conventionally been used. However, there have been problems such as the high cost of fabrication and the need for a large current density of around 10⁷Acm^-2 for magnetization reversal. The joint research group identified a region in the SRO thin film where very small RuO₆ lattice rotations of about 10 pm (10^-11m) occur, which dramatically increases the spin Hall effect, and revealed that a large SOT can be obtained even with a single magnet layer. This has enabled magnetization reversal at a current density of 3.1×10⁶Acm^-2, which is about one tenth of the conventional current density. This achievement provides a new guideline for material design, which actively utilizes the subtle “misalignment” of oxygen atoms in single crystals to control magnetization with low power consumption using SOT. It is expected to become a fundamental technology for next-generation spintronics devices such as ultra-low power-consumption magnetic memory and magnetic sensors that support artificial intelligence (AI), neuromorphic computing and automated driving systems. In addition to the University of Tokyo group and NTT, researchers from Japan Atomic Energy Agency, Hokkaido University and Kumamoto University joined the collaboration. The resulting paper has been published in the online edition of Advanced Materials.
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