F--Induced Tunable Perovskite Structure and Impressive Spin Polarization in SrCoO3

Tailoring the reciprocity between the charge and spin degrees of freedom in perovskites is effective in designing and realizing novel spintronic functionalities. Recently, it has been proposed that this type of quantum correlation can be intensively engineered via structure modulation, such as introducing protons into SrCoO3 and SmNiO3. To this end, we describe a new structure-modulating strategy via F- substitution, e.g., the perovskite oxyfluoride, SrCoO2.9-delta F0.1, against hexagonal Sr2Co2O5. Co K-edge X-ray absorption spectra reveal that a large amount of oxygen vacancies and a desirable structural distortion are generated with the evolution of the hexagonal to cubic structure induced by F- substitution at a low dose. Distinctively, SrCoO2.9-delta F0.1 demonstrates a much enhanced magnetic transition temperature of up to 350 K and realizes a remarkable exchange bias effect (H-EB = 1745 Oe) at room temperature that is driven by the strong interplay among the structure, oxygen vacancies, and charge and spin degrees of freedom. This work describes a simple F- substitution approach to design and regulate spintronics, which leads to a complex correlation among the order parameters by modulating oxygen vacancies.