Electrical transport and magnetic properties of a possible electron-doped layered manganese oxide

We report on the structural, transport, and magnetic properties of (Formula presented) thin films grown in vacuum by pulsed-laser deposition. The as-grown thin films have both the matrix (Formula presented) phase with (Formula presented) structure and an embedded MnO phase. The electrical transport and magnetic properties of the films are determined mainly by those of the matrix phase. By annealing, the as-grown thin films can be transformed into the normal (Formula presented) single phase, which shows the expected colossal magnetoresistance effect. Based on the composition of the matrix phase, and the structural, electrical, and magnetic properties of the films, we propose that the matrix phase is possibly electron doped with a mixed valence of (Formula presented) instead of the (Formula presented) as in the hole-doped case. © 2000 The American Physical Society.