Surface electronic phase transition in colossal magnetoresistive manganese perovskites:: La0.65Sr0.35MnO3

We have observed a distinct surface phase transition for an important class of giant magnetoresistance materials [La1-xSrxMnO3(x=0.35)]. The surface phase transition occurs at 240 K compared to 370 K for the bulk and is fundamentally different. In the bulk, a ferromagnetic metal to paramagnetic bad-metal transition occurs, while the lower-temperature surface transition is from an insulator to a semimetal. The surface of this manganese perovskite is electronically and compositionally quite different from the bulk with important implications for the behavior of artificially grown layered transition-metal oxides and for the use of surface sensitive techniques to probe the bulk. (C) 2000 American Institute of Physics. [S0003-6951(00)00630-6].