The researchers discovered the phenomenon in the material neodymium, an element that they described several years ago as a ‘self-induced spin glass’. Spin glasses are typically alloys where iron atoms for example are randomly mixed into a grid of copper atoms. Each iron atom behaves like a small magnet, or a spin. These randomly placed spins point in all kinds of directions.
Unlike conventional spin glasses, where there is random mixing of magnetic materials, neodymium is an element and without significant amounts of any other material, shows glassy behavior in its crystalline form. The spins form patterns that whirl like a helix, and this whirling is random and constantly changes.
Solid pattern when heated
In this new study, the researchers discovered that when they heated neodymium up from -268 C to – 265 C, the spins ‘freeze’ into a solid pattern forming a type of magnet, at the higher temperature. When cooling down the material, the random whirling helix patterns came back. ‘This ‘freezing’ of the pattern does not normally occur in magnetic material’, says Alexander Khajetoorians, professor of scanning probe microscopy at Radboud University.