Giant tunability of excitonic photoluminescence transitions in antiferromagnetic EuTe epilayers induced by magnetic polarons

EuTe layers with high purity, grown by molecular beam epitaxy, are investigated by magneto-optical spectroscopy. Low temperature photoluminescence (PL) experiments reveal narrow, exciton like emission peaks exhibiting a Stokes shift of View the MathML source. These emission peaks can be tuned over a giant range of View the MathML source by applying magnetic fields between zero and View the MathML source. The temperature dependence of the PL transition energies shows a kink at the antiferromagnetic-paramagnetic phase transition shifting to lower temperatures with increasing magnetic field. This unique magnetic field dependence as well as the temperature dependence of the PL transitions results from the formation of magnetic polarons, due to d–f exchange interactions between electrons in the conduction band and localized magnetic moments.