Defective Material Forms Spin Structures: JKU Physicists Explain & Surprising Experiment

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What is more important in research: theory or experiments? Ideally, both, as a collaboration between Johannes Kepler University Linz and the Max Planck Institute in Halle shows. The Linz physicists were able to provide the theoretical explanation for surprising results in experiments in Germany.

The German researchers had determined certain CrTe2 structures with X-ray spectroscopy - and came across skyrmions. These are tiny magnetic vortex nodes that behave like particles. They have relatively large spin structures that are quite insensitive to interfering influences. This makes them hopefuls for use as information carriers - in conventional storage units through to potential use in advanced quantum computers.

Unfortunately, skyrmions like to make themselves scarce. Only a few materials have the property to form such spin structures. CrTe2 is not one of them. Skyrmions actually only form when a material is magnetic but not centrosymmetric," explains Arthur Ernst from the Department of Many-Body Systems at JKU. Centrosymmetric (also called point symmetry) is a geometric figure when it is mapped onto itself by reflection at a symmetry point. Although CrTe2 has suitable magnetic properties, it is also centrosymmetric and therefore not a candidate for skyrmions - the German researchers were accordingly surprised by the discovery of the spin structures.

Defective system works better
Seeking advice, they turned to the Linz experts, who were indeed able to solve the puzzle. The samples used by the scientists in Halle were not completely pure - they contained defects.These defects broke the symmetry - and thus made the formation of the skyrmions possible," explains Ernst. Specifically, this defect is an excess of 30% of Cr atoms. "This violates the stichometry, i.e. the chemical composition is changed," Ernst explains.

His team is now developing methods to induce such symmetry-breaking effects in a targeted manner.This could be used to induce spin structures in many magnetic materials - and thus find new approaches for information storage media. You can see: Not every defect is a degradation," says the JKU physicist.

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