A dense distribution of classical spins in a conventional superconductor is expected to destroy the superconducting state. Tuning the coupling between the spins and the electronic spin density one finds that, as the coupling increases, the superconducting order parameter vanishes for a relatively small value of the coupling. However, for a moderate value of the coupling we find that a phase with superconducting correlations is stabilized, if we consider a Hubbard-like model with repulsive interactions. We also find that if we keep increasing the spin coupling, in the regime where the system is fully polarized, a local form of superconducting order arises, for some configurations of the classical spins. These are associated either to certain magnetic vortex structures or to a distribution of spins where some sites have no classical spin.

• Received 2 June 2007

DOI:https://doi.org/10.1103/PhysRevB.76.020510