Picosecond dynamics of magnetic polarons governed by energy transfer to the Zeeman reservoir

We suggest a mechanism of magnetic polaron formation in semimagnetic quantum wells in external magnetic fields, which is characterized by a transfer of energy from the carrier-magnetic-ions exchange reservoir to the Zeeman reservoir. This mechanism is related to the anisotropic exchange interaction due to the spin structure of the heavy-hole state. The polaron formation is determined by a precession of a total spin of magnetic ions inside the exciton volume in the sum of external and exchange field and happens inside the short time of about 10 ps. Experimentally, this mechanism manifests itself in photoluminescence spectra as an increase of the magnetic polaron shift at magnetic fields applied parallel to the quantum-well plane.