The magnetic properties of mono- and dierbium(Er) metallofullerenes have been studied by means of asynchrotron soft X-ray magnetic circular dichroism (SXMCD) technique. The effective magnetic moment ofthe Er ions has been estimated to be 8.48
B and is independent of the number of Er ions encapsulated insidethe fullerene cage. These Er metallofullerenes exhibit an antiferromagnetic-like behavior at low temperaturesthat is stronger in Er@C
82(
C2v isomer) monometallofullerene than in Er
2@C
82(
C2v) and Er
2C
2@C
82(
C2v)dimetallofullerenes. The result suggests that the unpaired spin on the monometallofullerene cages causes anindirect magnetic interaction between Er 4f spins of neighboring metallofullerenes. Furthermore, we havefound that the Weiss temperatures of the metallofullerene remain the same even when one of the Er ions inEr
2C
2@C
82(
Cs) is replaced by a nonmagnetic Y ion (i.e., ErYC
2@C
82). The results indicate that interactionbetween the two Er ions in the same fullerene cage does not contribute significantly to the overall magneticproperties.