  Hybrid structures synthesized from different materials have attracted
considerable attention because they may allow not only combination of the
functionalities of the individual constituents but also mutual control of their
properties. To obtain such a control an interaction between the components
needs to be established. For coupling the magnetic properties, an exchange
interaction has to be implemented which typically depends on wave function
overlap and is therefore short-ranged, so that it may be compromised across the
interface. Here we study a hybrid structure consisting of a ferromagnetic
Co-layer and a semiconducting CdTe quantum well, separated by a thin (Cd,Mg)Te
barrier. In contrast to the expected p-d exchange that decreases exponentially
with the wave function overlap of quantum well holes and magnetic Co atoms, we
find a long-ranged, robust coupling that does not vary with barrier width up to
more than 10 nm. We suggest that the resulting spin polarization of the holes
is induced by an effective p-d exchange that is mediated by elliptically
polarized phonons.
