Oxygen-deficiency-activated charge ordering in La2/3Sr1/3MnO3-delta thin films

The oxygen-deficiency-activated charge ordering (CO) transition has been ob served in C-oriented La2/3Sr1/3MnO3-delta thin films prepared by pulsed las er deposition on LaAlO3 substrates. A rapid growth of the sample resistivit y at temperatures below T-C is observed, while significant thermal hysteres is and electrical field induced transition from the insulator CO state to m etallic-like state are recorded. Such a CO state can also be partially melt ed under a magnetic field of 0.4 T, resulting in enhanced magnetoresistance at low temperatures. Magnetic properties of the films can be well understo od as the coexistence of the ferromagnetic state and the CO state. The CO s tate in oxygen deficient thin films is explained in terms of the Mn-O octah edral distortion or the narrowness of the conduction bandwidth of the e(g) carriers. (C) 2000 American Institute of Physics. [S0003-6951(00)04008-0].