Light Takes Center Stage in Unraveling Hidden Magnetic Secrets

The research conducted at the Hebrew University of Jerusalem challenges the widely accepted understanding of a fundamental principle of electromagnetism discovered by Michael Faraday in 1845. For nearly two centuries, it was believed that the rotation of light polarization in a magnetic field was solely due to the interaction of the light’s electric field with electric charges in matter. However, new research demonstrates that the magnetic field of light, long considered negligible, makes a direct and measurable contribution to this effect by interacting with spins.

Scientists, led by Dr. Amir Kapua and Binyamin Assulin from the Institute of Electrical Engineering and Applied Physics, used complex calculations to arrive at this conclusion. They discovered that the magnetic field of light contributes a significant 17% to the observed rotation in visible light, increasing to 70% in the infrared spectrum. Previously, these factors were considered insignificant in optical physics.

To verify their calculations, the scientists applied their model to a terbium gallium garnet (TGG) crystal, commonly used to measure the Faraday effect. The model confirmed that the magnetic component plays a crucial role in the interaction, especially at longer wavelengths. Dr. Kapua explained: «This is an interaction between light and magnetism. A static magnetic field ‘twists’ light, and light, in turn, reveals the magnetic properties of the material. We found that the magnetic part of light exerts a first-order effect, surprisingly active in this process.» Binyamin Assulin noted that the results indicate that light ‘talks’ to matter through its magnetic field-a channel of interaction largely ignored until now. «In other words, light not only illuminates matter but exerts magnetic influence on it,» added Kapua.

This discovery opens up new prospects in optics and magnetism, including applications in spintronics (an area of electronics that uses the spin of electrons for information transmission and storage), optical data storage, and the management of magnetism through light. It may even contribute to future spin-based quantum computing technologies, which demand precise control over magnetic states. Recent advancements in spintronics have highlighted the potential of manipulating electron spin with light, paving the way for ultrafast data processing and innovative magnetic storage solutions. Furthermore, the integration of light in managing magnetic states could offer novel approaches for enhancing data security and storage capacity.