Swiss researchers have developed a new technique that enables magnetic polarity changes using only a laser beam, an advancement with major potential for creating adaptable electronic circuits.
Using a special ferromagnet, researchers at the University of Basel and ETH Zurich were able to manipulate magnetic polarity using laser light, without any additional heating. The results were reported in a recent paper published in Nature, showcasing a major advancement that can produce different magnetic polarities at separate points within a single piece of material.
Ferromagnets Explained
Ferromagnets are the most common types of magnets used in our everyday world. They operate on the synchronized spin of electrons, all rotating in the same direction. That unanimous spin direction generates their magnetic power, allowing magnets to stick to metal and compasses to point toward the Earth’s magnetic poles.
However, this is only true below a certain temperature threshold. Inside magnets is also a chaotic thermal motion that remains ever-present. When the magnets are relatively cool, this motion is weak, allowing the electron interactions to overcome it and generate the synchronized spin. By contrast, above a certain temperature, the thermal motion becomes so powerful that it overrides the electrons’ synchronization, introducing larger-scale chaos that causes the material to lose its ferromagnetism.
That threshold is typically used to intentionally alter the polarity of a ferromagnetic material. Once the heated magnet begins to cool, its electrons again order themselves into a synchronized spin, typically in a different direction.
The new research by researchers at the University of Basel and ETH Zurich changes all of this, altering the polarity without applying any heat.
Constructing a Laser Switchable Magnet
“What’s exciting about our work is that we combine the three big topics in modern condensed matter physics in a single experiment: strong interactions between the electrons, topology and dynamical control,” said co-author Prof. Dr. Ataç Imamoğlu of ETH in Zurich.
The researchers built their laser switchable magnet from two thin, but slightly twisted layers of the organic semiconductor molybdenum ditelluride. Their two-layer material allowed topological states to form—that is, quantum states that are permanently defined and cannot be altered by small local disturbances.
Experiments revealed that the material’s electrons existed in tunable topological states that could be manipulated from insulating to conducting. More intriguingly, both states feature parallel aligned electron spins, turning the material into a ferromagnet.
“Our main result is that we can use a laser pulse to change the collective orientation of the spins,” says Olivier Huber, a PhD candidate at ETH.
Hellbound and Down 