Fachgruppe Nanostrukturierte Materialien    

We report the fabrication and characterization of self assembled CdSe quantum dots embedded in a dilute magnetic (Zn,Mn,Be)Se barrier. Transport experiments indicate a finite spin splitting at zero magnetic field although the materials are intrinsically paramagnetic. The result can be explained by the formation of a single magnetic polaron by ferromagnetic interaction between the surrounding Mn ions mediated by the carriers inside the dot. The effect prevails up to relatively high temperatures which we ascribe to a feedback mechanism induced by the tunneling current, previously predicted theoretically.