Lower temperatures cause reduced mobility of tiny components in almost all materials. When there is a lack of heat energy, atoms are less likely to change their location or magnetic moments’ direction: they freeze. For the first time, a group of scientists has seen the opposite behavior in a nickel oxide material related to high-temperature superconductors. When this nickelate cools, the fluctuations get faster rather than freezing. The scientists observed them using x-ray correlation spectroscopy. The coherent soft x-rays allowed them to follow the order of elementary magnetic moments (spin dynamics) in space and time.
This finding could aid in the understanding of high-temperature superconductivity in copper oxides (cuprates). The research reveals that coherent soft x-rays may be used to examine materials that are spatially non-uniform, especially those that gain new functionality as a result of this non-uniformity.
Future x-ray sources, such as BESSY III, will produce many orders of magnitude more intense coherent x-ray radiation than current sources, allowing this spectroscopy technique to be extended to faster fluctuations (spin dynamics) and shorter length scales.