A Surface Insulator-to-Conductor Phase Transition in Colossal Magnetoresistive Manganese Perovskites Thin Films

Abstract

We have observed a distinct surface phase transition for an important class of colossal magnetoresistive materials, La 0.65 D 0.35 MnO 3 (with D = Sr, Pb) occurring in a surface layer compositionally different from the bulk. The surface phase transition occurs around 240 K compared to 350 K for the bulk and is fundamentally different. In the bulk, a ferromagnetic metal to paramagnetic 'bad metal' occurs, while the lower-temperature surface transition is from an n-type (in case of La 0.