For nearly two centuries, scientists have believed that only the electric side of light played a role in certain magnetic effects.
Now, a new study from the Hebrew University of Jerusalem has turned that idea on its head.
Researchers have discovered that the magnetic component of light also has a direct and powerful influence on matter in the well-known Faraday effect.
This surprising finding opens the door to new advances in optics, data storage, and emerging quantum technologies.
The Faraday effect was first discovered in 1845 by the British scientist Michael Faraday. It describes what happens when a beam of light passes through a material that is placed in a strong magnetic field.
As the light travels through the material, its polarization, or the direction in which it vibrates, slowly rotates.
For more than 180 years, this effect was explained only in terms of the light’s electric field interacting with charged particles inside the material. The weaker magnetic field that travels with light was considered too small to matter.
Dr. Amir Capua and Benjamin Assouline, from the Institute of Electrical Engineering and Applied Physics at the Hebrew University of Jerusalem, challenged this long-standing assumption.
Their new study, published in the journal Scientific Reports, provides the first solid theoretical proof that the magnetic field of light contributes directly to the Faraday effect. In simple terms, light does not just shine on materials, it can also influence them magnetically.
Light is made up of both electric and magnetic waves that move together through space.
When a constant magnetic field is applied to a material and light passes through it, the light is “twisted” in a way that reveals the magnetic properties of that material.
What Capua and Assouline found is that the tiny magnetic wave inside the light itself helps create this twisting motion. It acts on the spinning particles inside the material and produces a kind of magnetic push, known as a torque, similar to what a regular magnet would do.
To test and measure this effect, the researchers focused on a special crystal called Terbium Gallium Garnet, or TGG. This material is commonly used in experiments involving the Faraday effect.
Their calculations showed that the magnetic part of light is responsible for about 17 percent of the rotation seen in visible light. In the infrared range, its contribution becomes even more important, reaching up to 70 percent of the total effect.
This discovery changes how scientists understand the interaction between light and matter. It suggests that light “talks” to materials in more ways than previously believed, using both its electric and magnetic components.
The findings could lead to new technologies in spintronics, where the tiny spins of particles are used to store and process information, as well as in optical data storage and future quantum computing systems.
By revealing the hidden magnetic influence of light, this study not only rewrites a chapter of physics history but also opens up exciting possibilities for the technologies of tomorrow.
