Anomalous Hall effect and re-entrant metallic transitions in epitaxial PrNiO3-δ thin films

We have deposited and studied epitaxial PrNiO3-δ thin films (12 nm) for the temperature dependent resistivity and the anomalous Hall effect. The post-deposition in situ oxygen annealing time for thin film formation was varied (0 to 5 min) in order to change the oxygen stoichiometry. One film was kept completely unannealed to create oxygen deficiency. A decrease in resistivity was observed with increasing oxygen-annealing time. In spite of different oxygen content and resistivity values, all the other films show metal to insulator transitions at the same temperature (∼100 K), except the unannealed insulating film. Before a complete insulating state was established while cooling, a re-entrant metallic state appeared at lower temperatures, where the on-set temperature was different for different films. A nonlinear magnetic-field dependence of Hall resistance manifests in the low-temperature re-entrant metallic state in contrast to the normal Hall effect in the high-temperature metallic state. The theoretical fits to temperature dependent resistivity indicate a non-Fermi liquid behavior in the high temperature metallic state. Moreover, the non-Fermi liquid behavior gets modified by the variation in oxygen content in PrNiO3-δ films.