We carry out a first-principles study of stoichiometric heterostructures composed of polar oxide ${\text{LaAlO}}_3$ and ferromagnetic semiconductor EuO. We show that electrostatic doping achieved by an electric field in the polar oxide leads to a fully spin-polarized two dimensional electron gas at the interface. This mechanism contrasts with a previous calculation of the ${\text{LaAlO}}_3/\text{EuO}$ interface in which electron doping is introduced through a nonstoichiometric ${\text{LaAlO}}_3$ layer. Our system allows a low level of doping in EuO that is comparable to the Gd-doped EuO found in recently reported experiment, and is thickness controllable. We predict a change of magnetic moment of Eu and increase of the Curie temperature in the doped layers of EuO.

• Received 21 June 2010

DOI:https://doi.org/10.1103/PhysRevB.82.235305