  The electromagnetic vacuum energy is considered in the presence of a
perfectly conducting plane and a ball with dielectric permittivity
$\varepsilon$ and magnetic permeability $\mu$, $\mu\ne1$. The attention is
focused on the Casimir repulsion in this system caused by magnetic permeability
of the sphere. In the case of perfectly permeable sphere, $\mu=\infty$, the
vacuum energy is estimated numerically. The short and long distance asymptotes
corresponding to the repulsive force and respective low temperature corrections
and high temperature limits are found for a wide range of $\mu$. The
constraints on the Casimir repulsion in this system are discussed.
