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Advance in opto-magnetic technology leads to five-fold increase in torque efficiency

Breakthrough in opto-magnetic technology: 5-fold increase in torque efficiency
When circularly polarized light is incident perpendicular to the surface of a nano-thin film of cobalt-platinum alloy, which consists of cobalt and platinum, an opto-magnetic torque is generated (red and blue vectors) that changes the magnetization direction (black vector). The opto-magnetic torque consists of components out-of-plane (red vector) and in-plane (blue vector). Credit: Nukui et al.

Researchers at Tohoku University have achieved a significant advancement in opto-magnetic technology, observing an opto-magnetic torque approximately five times more efficient than in conventional magnets. This breakthrough, led by Koki Nukui, Assistant Professor Satoshi Iihama, and Professor Shigemi Mizukami, has far-reaching implications for the development of light-based spin memory and storage technologies.

Opto-magnetic is a method which can generate force on magnets. This can be used to change the direction of magnets by light more efficiently. By creating alloy nanofilms with up to 70% platinum dissolved in cobalt, the team discovered that the unique relativistic quantum mechanical effects of platinum significantly boost the magnetic torque.

The study revealed that the enhancement of opto-magnetic torque was attributed to the electron generated by circularly polarized light and relativistic quantum mechanical effects. The findings are in Âé¶¹ÒùÔºical Review Letters.

This achievement allows for the same opto-magnetic effect to be produced with only one-fifth of the previous light intensity, paving the way for more energy-efficient opto-magnetic devices.

Breakthrough in opto-magnetic technology: 5-fold increase in torque efficiency
Examples of experimental data on magnetization oscillation driven by opto- magnetic torque measured by the pump-probe time-resolved magneto-optical Kerr effect: (a) Cobalt nano-thin film; (b) Cobalt-Platinum nano-thin film (Platinum concentration is 65% atomic ratio); (c) Platinum concentration dependence of the magnitude of opto-magnetic torques evaluated from the measured magnetization oscillations. Both the in-plane and out-of-plane torques increase with the platinum concentration. Credit: Nukui et al.

The findings not only provide new insights into the physics of electron orbital angular momentum in metallic magnetic materials but also contribute to the development of high-efficiency spin memory and storage technologies that use light to write information.

"These improvements could result in faster and more energy-efficient devices in the future," explains Mizukami.

The research aligns with the growing interest in opto-electronic fusion technologies, combining electronic and optical technologies for next-generation applications. This discovery marks a significant step forward in controlling nanomagnetic materials using light and magnetism.

More information: Koki Nukui et al, Light-Induced Torque in Ferromagnetic Metals via Orbital Angular Momentum Generated by Photon Helicity, Âé¶¹ÒùÔºical Review Letters (2025). . On arXiv:

Provided by Tohoku University

Citation: Advance in opto-magnetic technology leads to five-fold increase in torque efficiency (2025, February 6) retrieved 21 May 2025 from /news/2025-02-advance-opto-magnetic-technology-torque.html
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