Influence of Chemical Doping on the Magnetic Properties of EuO

We report on the magnetic field dependence of the apparent ferromagnetic ordering temperature (T-F) of the ferromagnetic semiconductor EuO doped with 8% Gd, La, or Lu. Chemical doping is a common method to increase the T-F of EuO. Recent findings demonstrate that in thin films only a fraction of the dopants donate electrons into the conduction band. We show that the T-F of doped EuO determined by the standard procedure drastically increases with applied magnetic fields. The comparison of measured data to theoretical models is in agreement with large fractions of dopant electrons being localized and the presence of magnetic disorder. DOI: 10.1103/PhysRevB.87.014416