Perpendicular magnetic anisotropy via strain-engineered oxygen vacancy ordering in epitaxial La1−xSrxCoO3−δ

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Tuning oxygen vacancy concentrations is a well-established approach to controlling properties of complex oxides. Recent work on perovskite cobaltites has shown that ordering of oxygen vacancies can also be tuned, via heteroepitaxial strain, presenting new opportunities. Here we demonstrate that strain-engineered vacancy ordering can control and enhance magnetic anisotropy in $\mathrm{L}{\mathrm{a}}_{1\ensuremath{-}x}\mathrm{S}{\mathrm{r}}_{x}\mathrm{Co}{\mathrm{O}}_{3\ensuremath{-}\ensuremath{\delta}}$. In particular, in-plane oxygen vacancy order induced by compressive strain is shown to result in remarkably strong perpendicular magnetic anisotropy, with anisotropy constant up to $6\ifmmode\times\else\texttimes\fi{}{10}^{6}\phantom{\rule{0.16em}{0ex}}\mathrm{erg}/\mathrm{c}{\mathrm{m}}^{3}$. The anisotropy is thickness independent, ruling out surface and film/substrate interface anisotropy, but strongly correlated with lateral coherence of defect order from electron microscopy. The results are discussed in terms of the unit-cell-level superlattice induced by the oxygen vacancy order, generating intriguing analogies with metal-based multilayer systems. Generally, this Rapid Communication highlights the significant potential of strain-based manipulation of oxygen vacancy ordering to control and enhance complex oxide properties.