Robust magnetic polarons in type-II (Zn, Mn) Te/ZnSe magnetic quantum dots

We present a magneto-optical study of magnetic polarons in type-II (Zn, Mn) Te quantum dots. The polarons are formed due to the exchange coupling between the spins of the holes and those of the Mn ions, both of which are localized in the dots. In our photoluminescence studies, the magnetic polarons are detected at temperatures up to similar to 150 K, with a formation energy of similar to 40 meV. The emission from these dots exhibits an unusually small Zeeman shift with applied magnetic field (similar to 2 meV at 8 T) and at the same time a very large circular polarization. We attribute this apparently contradictory behavior by a low and weakly temperature-dependent magnetic susceptibility due to antiferromagnetic coupling of the Mn spins.