Self consistent renormalization theory of itinerant ferromagnets is used to
calculate the Curie temperature of clusters down to approximately 100 atoms in
size. In these clusters the electrons responsible for the magnetic properties
are assumed to be (weakly) itinerant. It is shown that the Curie temperature
can be larger than in the bulk. The effect originates from the phenomenon of
level repulsion in chaotic quantum systems, which suppresses spin fluctuations.
Since the latter destroy the magnetic order the resulting Curie temperature
increases, contrary to expectations of the naive Stoner picture. The
calculations are done assuming that the energy levels of the cluster are
described by the Gaussian Orthogonal Ensemble of random matrix theory.Comment: Phys. Rev. B, accepted for publicatio