  We present a study on low-$T_c$
superconductor-insulator-ferromagnet-superconductor (SIFS) Josephson junctions.
SIFS junctions have gained considerable interest in recent years because they
show a number of interesting properties for future classical and quantum
computing devices. We optimized the fabrication process of these junctions to
achieve a homogeneous current transport, ending up with high-quality samples.
Depending on the thickness of the ferromagnetic layer and on temperature, the
SIFS junctions are in the ground state with a phase drop either 0 or $\pi$. By
using a ferromagnetic layer with variable step-like thickness along the
junction, we obtained a so-called 0-$\pi$ Josephson junction, in which 0 and
$\pi$ ground states compete with each other. At a certain temperature the 0 and
$\pi$ parts of the junction are perfectly symmetric, i.e. the absolute critical
current densities are equal. In this case the degenerate ground state
corresponds to a vortex of supercurrent circulating clock- or counterclockwise
and creating a magnetic flux which carries a fraction of the magnetic flux
quantum $\Phi_0$.
