Oxygen-Deficiency-Activated Anomalous Transport In La2/3sr1/3mno3-Delta Thin Films Deposited By Laser Ablation

The transport in oxygen-deficient polycrystalline La2/3Sr1/3MnO3-delta thin films deposited on Si(l 11) 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.