  The observation of spin-related phenomena of microcavity polaritons has been
limited due to weak Zeeman effect of non-magnetic semiconductors. We
demonstrate that the incorporation of magnetic ions into quantum wells placed
in a non-magnetic microcavity results in enhanced effects of magnetic field on
exciton-polaritons. We show that in such a structure the Zeeman splitting of
exciton-polaritons strongly depends on the photon - exciton detuning and
polariton wavevector. Our experimental data are explained by a model where the
impact of magnetic field on the lower polariton state is directly inherited
from the excitonic component, and the coupling strength to cavity photon is
modified by external magnetic field.
