Electric field control of ordered oxygen vacancy planes and antiferromagnetic structures in strontium cobaltite

The polarized ionic liquids (ILs) could generate intense electric fields on the surface of solid-state materials and create functional defects by ion migration within them, resulting in phase transitions of metal-insulator or paramagnet-ferromagnet, etc. Such a strong electric field even provides an opportunity for the control of spin ordering in antiferromagnetic (AFM) crystal which is difficult to be manipulated due to the strong exchange coupling between antiparallel spins in the whole bulk. Here we find that the ferromagnetic SrCoO₃of 40 nm could be transformed to AFM SrCoO_2.5with ordered oxygen vacancy planes either vertical (V-SrCoO_2.5) or parallel (P-SrCoO_2.5) to the surface by IL gating. The spin Hall magnetoresistances suggest that the AFM easy axes of V- and P-SrCoO_2.5are along [010] and11¯0, respectively. The orientations of gating induced oxygen vacancy planes are related to the oxygen framework rotation in the parent SrCoO₃and could be controlled by the strain engineering. Our results not only supply a novel way to manipulate the AFM spins by creating functional ordered defects, but also reveal the effect of oxygen framework rotation on the formation of oxygen vacancies under ionic liquid gating.