Shedding Light on Quantum Magnets

Osaka Metropolitan University and University of Tokyo scientists successfully used light to visualize tiny magnetic regions, or magnetic domains, in a specialized quantum material. They also manipulated these regions using an electric field. Magnets that don’t stick to metal surfaces include antiferromagnets, magnetic materials in which magnetic forces, or spins, point in opposite directions, cancel each other out, and result in no net magnetic field. They don’t behave like traditional ferromagnets.

Antiferromagnets with quasi-one-dimensional quantum properties, whereby magnetic characteristics are mainly confined to one-dimensional chains of atoms, are candidates for next-generation electronics and memory devices.

“Observing magnetic domains in quasi-one-dimensional quantum antiferromagnetic materials has been difficult due to their low magnetic transition temperatures and small magnetic moments,” according to Kenta Kimura, an associate professor at Osaka Metropolitan University and lead author of the study, published in Physical Review Letters.

The researchers took a creative look at the quasi-one-dimensional quantum antiferromagnet BaCu₂Si₂O₇. They took advantage of nonreciprocal directional dichroism, where the light absorption of a material changes upon the reversal of the direction of light or its magnetic moments, enabling them to visualize magnetic domains within BaCu₂Si₂O₇. Opposite domains coexist within a single crystal, and their domain walls are primarily aligned along specific atomic chains, or spin chains. They also demonstrated that domain walls can be moved using an electric field, thanks to a phenomenon called magnetoelectric coupling, where magnetic and electric properties are interconnected.

The study opens up possibilities for technological applications and exploring new frontiers in physics that could lead to the development of future quantum devices and materials.