Degradation of LaMnO3−y surface layer in LaMnO3−y/metal interface

We report electrical measurements showing the degradation processes of LaMnO3−y (LaMnO) in LaMnO/normal metal interface in both point contact and planar-type junctions. The time evolution of the junction resistance is characterized by the appearance of a second maximum in the resistance versus temperature dependence (R–T) that occurs at a temperature lower than that for the metal–insulator transition in the bulk. These effects are explained in terms of the formation of a depleted interface layer in LaMnO caused by an out-diffusion of oxygen from the manganite surface to the normal metal. This was confirmed by XPS measurements. Similar results on LaSrMnO3−y/metal interfaces were also obtained.