Magnetism of 3d transition metal nanoparticles on surfaces probed with synchrotron radiation – from ensembles towards individual objects

Mass‐filtered Fe, Co and FeCo nanoparticles in the size regime from 7 to 25 nm have been deposited under soft‐landing conditions onto ferromagnetic films, non‐magnetic surfaces as well as embedded into Al matrices. In situ X‐ray magnetic circular dichroism (XMCD) measurements reveal a ferromagnetic behaviour of FeCo nanoparticles (size: 10 nm) on Si‐substrates at room temperature whereas the respective Co nanoparticles are superparamagnetic. Besides measurements on ensembles of nanoparticles, we have also carried out in situ measurements on individual Fe nanoparticles using X‐ray photoemission electron microscopy at the Fe L3,2 edges. Fe nanoparticles on Co films show a magnetic contrast depending on the direction of the underlying poly‐crystalline Co domains. This technique also allows to record XMCD spectra on individual nanoparticles. Spectroscopy and spectro‐microscopy on magnetic particles. magnified image