An international team of physicists from Bielefeld University, Uppsala University, the University of Strasbourg, University of Shanghai for Science and Technology, Max Planck Institute for Polymer Research, ETH Zurich, and the Free University Berlin have developed a precise method to measure the ultrafast change of a magnetic state in materials. They do this by observing the emission of terahertz radiation that necessarily accompanies such a magnetization change. Their study, titled "Ultrafast terahertz magnetometry," is being published today in Nature Communications.