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

Abstract

We report on the structural, transport, and magnetic properties of La_0.67Sr_0.33MnO_x thin films grown in vacuum by pulsed-laser deposition. The as-grown thin films have both the matrix La_1.34Sr_0.66MnO₄ phase with K₂NiF₄ 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 La_0.67Sr_0.33MnO₃ 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 Mn²⁺/Mn³⁺ instead of the Mn³⁺/Mn⁴⁺ as in the hole-doped case.