Low-temperature properties of strongly correlated nanoclusters in the presence of magnetic field

Nano-sized particles and clusters exhibit different thermal and magnetic properties from both individual atoms and bulk properties in a material. We have used exact diagonalization calculations to study the specific heat, the susceptibility and short-range spin-spin correlations at low temperature in the present of an external magnetic field. The calculations reveal that the external magnetic field and the energy spacing $\Delta $ in the conduction band tune the interplay between the \textit{local} Kondo and \textit{non local} RKKY interactions. The field-induced level crossing of the low-lying many-body states gives rise to a rich magnetic behavior of the nanoclusters. We find a transition from antiferromagnetic to ferromagnetic state as the cluster size is reduced. This may be relevant to experimental realizations of small rings or isolated quantum dots with tunable magnetic properties.