  We present photoluminescence studies of CdTe and CdMnTe quantum dots grown in
two adjacent layers. We show that when the dots are 8 nm apart, their
magnetooptical properties - Zeeman shifts and transition linewidths - are
analogous to those of individual CdTe or CdMnTe dots. When the dots are grown
closer, at a distance of 4 nm, it becomes possible to tune the electron states
to resonance and obtain a formation of a molecular state hybridized over the
two dots. As a result of the resonant enhancement of the electron-Mn ion
exchange interaction, spectroscopic signatures specific to spin-dependent
inter-dot coupling appear. Namely, an anomalous increase of the Zeeman shift
and a resonant increase in the transition linewidth are observed. A simple
model calculation allows us to quantitatively reproduce the experimental
results.
