Researchers Uncover a Novel and Peculiar Pype of Magnetism

Researchers from ETH Zurich have identified a previously unseen type of magnetism. Experiments reveal that an artificially created material exhibits magnetism through a mechanism not observed before.

The widely recognized form of magnetism, known as ferromagnetism (the type that causes items to stick to your fridge), occurs when the spins of all electrons in a material align in the same direction. However, there are alternative forms, such as paramagnetism, a weaker version occurring when electron spins point in random directions.

Discovery of Unconventional Magnetism in Moiré Materials

In the recent investigation, ETH scientists identified an unconventional form of magnetism. The research focused on the magnetic characteristics of moiré materials, experimental substances created by layering two-dimensional sheets of molybdenum diselenide and tungsten disulfide. These materials possess a lattice structure capable of housing electrons.

To discern the type of magnetism exhibited by these moiré materials, the team introduced electrons by applying an electrical current and gradually increasing the voltage. To gauge its magnetism, they directed a laser at the material and measured the intensity of light reflection for various polarizations. This process helps determine whether the electron spins align in the same direction (indicating ferromagnetism) or if they are oriented randomly (suggesting paramagnetism).

At first, the material displayed paramagnetism, but with the gradual addition of electrons to the lattice, an abrupt and unexpected transformation took place, turning it into a ferromagnetic state. Interestingly, this shift precisely coincided with the lattice reaching a capacity beyond one electron per lattice site, eliminating the exchange interaction as the typical mechanism driving ferromagnetism.

Ataç Imamoğlu, the lead author of the study, remarked, “This provided compelling evidence for a novel form of magnetism that defies explanation through the exchange interaction.”

Emergence of Ferromagnetism through Doublon Formation and Kinetic Magnetism

The research team put forth an alternative explanation: when more than one electron occupies the lattice sites, they form pairs known as “doublons,” which, through quantum tunneling, fill the entire lattice. During this process, the electrons minimize their kinetic energy by aligning their spins, resulting in the emergence of ferromagnetism. This form of “kinetic magnetism” has been theoretically predicted for many years but has not been observed in solid materials until now.

The scientists intend to delve deeper into this phenomenon, exploring its characteristics, including whether it can be replicated at higher temperatures. It’s worth noting that, for this experiment, the material had to be cooled down to a fraction above absolute zero.

Read the original article on: New Atlas

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