Magnetism in Mn clusters: Role of correlation effects

The effects of the electronic correlations on metallic Mn13 icosahedral clusters are investigated in terms of single-band Hubbard model at half-band filling. The ground state, the spin-flip energy, and the two-body spin-correlation functions are calculated exactly using a Lanczos diagonalization scheme. Our theory provides a natural framework to understand the different density-functional magnetic arrangements for Mn13 clusters, recently predicted in the literature.