Oxygen-deficiency-activated anomalous transport in La2/3Sr1/3MnO3−δ thin films deposited by laser ablation

The transport in oxygen-deficient polycrystalline La2/3Sr1/3MnO3−δ thin films deposited on Si(111) substrates using laser ablation is studied by measuring the resistivity and ac magnetic susceptibility over the range 2–300 K. The oxygen deficiency results in a serious shift of the insulating–metal (IM) transition toward the low-temperature side and anomalous transport behaviour over the low-temperature range. The ac susceptibility measurement reveals that, upon cooling, the sample exhibits a ferromagnetic transition, a weak anomaly at the IM transition and an antiferromagnetic (AFM) transition which may mainly arise from the charge ordering. Partial melting of the AFM state under a low magnetic field of 750 Oe is observed at 4.2 K.