A team of researchers from the Helmholtz-Zentrum Berlin (HZB) and the University of Potsdam has investigated heat transport in a model system comprising nanometre-thin metallic and magnetic layers. Similar systems are candidates for future high-efficiency data storage devices that can be locally heated and rewritten by laser pulses (heat-assisted magnetic recording). Measurements taken with extremely short X-ray pulses have now shown that the heat is distributed 100 times slower than expected in the model system. The results are published in Nature Communications.