  We have investigated the nucleation of superconductivity in an Al mesoscopic
disk, with a magnetic dot on the top. The dot is magnetized perpendicularly,
and its magnetic field is inhomogeneous. The Al disk and magnetic dot are
separated by an insulating layer, which ensures that there is only magnetic
interaction between them. This hybrid superconductor/ferromagnet structure
exhibits the maximum critical temperature for a finite value of the
perpendicular applied magnetic field, which is parallel to the magnetization of
magnetic dot. We have found a good agreement between the experimental data for
the superconductor/normal metal phase boundary and the theoretical predictions
based on the Ginzburg-Landau theory.

Superconductivity;Mesoscale and Nanoscale Physics