Electronic and magnetic properties of the La$_{0.7}$Sr$_{0.3}$MnO$_{3}$/SrTiO$_{3}$ interface from first principles calculations

We present results of first principles calculations of the electronic and magnetic properties of the La$_{0.7}$Sr$_{0.3}$MnO$_3$/SrTiO$_{3}$ interface. We are interested in the changes with respect to the bulk as concerns ferromagnetism and half-metallicity. The bulk calculations give a nearly half-metallic ground state for the manganite. In transport the system is predicted to be totally half-metallic. This latter property is preserved at the interface only if the magnetic coupling between the interface region and the bulk is ferromagnetic. We have looked at the two possible interface terminations between La$_{0.7}$Sr$_{0.3}$MnO$_3$ and SrTiO$_{3}$ and found that one of the interfaces preserves the bulk properties of La$_{0.7}$Sr$_{0.3}$MnO$_3$ whereas the other type of termination suppresses them. Reducing the number of holes at the interface by introducing LaMnO$_{3}$ restores ferromagnetism. Hence the possibility of engineering interfaces to improve the Tunneling Magneto-Resistance yield in the La$_{0.7}$Sr$_{0.3}$MnO$_3$/SrTiO$_{3}$/La$_{0.7}$Sr$_{0.3}$MnO$_3$ tunnel junctions.