  Owing to their integer spin, exciton-polaritons in microcavities can be used
for observation of non-equilibrium Bose-Einstein condensation in solid state.
However, spin-related phenomena of such condensates are difficult to explore
due to the relatively small Zeeman effect of standard semiconductor microcavity
systems and the strong tendency to sustain an equal population of two spin
components, which precludes the observation of condensates with a well defined
spin projection along the axis of the system. The enhancement of the Zeeman
splitting can be achieved by introducing magnetic ions to the quantum wells,
and consequently forming semimagnetic polaritons. In this system, increasing
magnetic field can induce polariton condensation at constant excitation power.
Here we evidence the spin polarization of a semimagnetic polaritons condensate
exhibiting a circularly polarized emission over 95% even in a moderate magnetic
field of about 3 T. Furthermore, we show that unlike nonmagnetic polaritons, an
increase on excitation power results in an increase of the semimagnetic
polaritons condensate spin polarization. These properties open new
possibilities for testing theoretically predicted phenomena of spin polarized
condensate.
