Local magnetism in rare-earth metals encapsulated in fullerenes

Local magnetic properties of rare-earth (RE) atoms encapsulated in fullerenes have been characterized using x-ray magnetic circular dichroism and x-ray absorption spectroscopy (XAS). The orbital and spin contributions of the magnetic moment have been determined through sum rules and theoretical model calculations, and have been found to be highly reduced compared to those of the corresponding free RE³⁺ ions. Crystal-field and hybridization effects have been investigated by the way of calculations to simulate the effect of the carbon cage on the RE; both hypotheses have reproduced the experimental spectra resulting also in a significant reduction of the orbital and spin moments. While isotropic XAS spectra have confirmed a roughly trivalent state for the RE metals, a back electron transfer from the cage to the metal has been quantified. A paramagnetic coupling has been found between the metal centers from 6 K to 300 K.