Element-Specific Magnetic Properties of Di-Erbium Er₂@C₈₂ and Er₂C₂@C₈₂ Metallofullerenes: A Synchrotron Soft X-ray Magnetic Circular Dichroism Study

Abstract

The magnetic properties of mono- and dierbium(Er) metallofullerenes have been studied by means of a synchrotron soft X-ray magnetic circular dichroism (SXMCD) technique. The effective magnetic moment of the Er ions has been estimated to be 8.48 μB and is independent of the number of Er ions encapsulated inside the fullerene cage. These Er metallofullerenes exhibit an antiferromagnetic-like behavior at low temperatures that is stronger in Er@C82(C2v isomer) monometallofullerene than in Er2@C82(C2v) and Er2C2@C82(C2v) dimetallofullerenes. The result suggests that the unpaired spin on the monometallofullerene cages causes an indirect magnetic interaction between Er 4f spins of neighboring metallofullerenes. Furthermore, we have found that the Weiss temperatures of the metallofullerene remain the same even when one of the Er ions in Er2C2@C82(Cs) is replaced by a nonmagnetic Y ion (i.e., ErYC2@C82). The results indicate that interaction between the two Er ions in the same fullerene cage does not contribute significantly to the overall magnetic properties.