Re-entrance to a ferromagnetic insulator with oxygen-vacancy ordering in the La0.7Sr0.3MnO3/SrTiO3 superlattice

Abstract

The charge-density wave is correlated with the properties in transition metal oxides, and regulating this state is important to explore the potential of oxides. Defects could modulate the local environment, in which the effect is subject to the concentration and arrangement, and an artificial arrangement of defect-ordering is highly expected to design the material properties. In this work, the ordering of oxygen vacancies with a preferred location on the (001) La/SrO plane by self-structural optimization was induced in La_0.7Sr_0.3MnO₃/SrTiO₃ superlattices with medium oxygen pressure during SrTiO₃ deposition, and then the ferromagnetic charge-ordering (CO)/charge-density-wave (CDW) state was formed in La_0.7Sr_0.3MnO₃ with susceptibility to magnetic field, temperature, and superlattice configuration. In addition, re-entrance to the ferromagnetic insulator CO/CDW could be induced by a high magnetic field. The selective occupancy of oxygen vacancies on the (001) La/SrO plane and the phase fluctuation around the CO/CDW-to-ferromagnetic metal phase transition were critical to the above properties. The interfacial diffusion with atomic-level resolution to control oxygen vacancies could be used in other magnetoelectric systems and corresponding device applications.