  Combining experiments with first principles calculations, we show that
site-specific doping of Mn into SrTiO3 has a decisive influence on the
dielectric properties of these doped systems. We find that phonon contributions
to the dielectric constant invariably decrease sharply on doping at any site.
However, a sizable, random dipolar contribution only for Mn at the Sr site
arises from a strong off-centric displacement of Mn in spite of Mn being in a
non-d0 state; this leads to a large dielectric constant at higher temperatures
and gives rise to a relaxor ferroelectric behavior at lower temperatures. We
also investigate magnetic properties in detail and critically reevaluate the
possibility of a true multi-glass state in such systems.
