Electronic phase separation in manganite-insulator interfaces

Using a realistic microscopic model, we study the electric and magnetic properties of the interface between a half-metallic manganite and an insulator. We find that the lack of carriers at the interface attenuates the double-exchange mechanism, weakening the ferromagnetic coupling between the Mn ions. In this situation the ferromagnetic order of the Mn spins near the interface is unstable against antiferromagnetic CE correlations, and a separation between ferromagnetic-metallic and antiferromagnetic-insulator phases at the interfaces can occur. We obtain the result that the insertion of extra layers of undoped manganite at the interface introduces extra carriers which reinforce the double-exchange mechanism and suppress antiferromagnetic instabilities.