Controlling Magnetism and Transport at Perovskite Cobaltite Interfaces via Strain-Tuned Oxygen Vacancy Ordering

Abstract

Complex oxides such as perovskite cobaltites exhibit rich phenomena at interfaces due to the complex interplay between their structural, defect, electronic, and magnetic degrees of freedom. We study this here in the ferromagnetic metallic cobaltite La1-xSrxCoO3-, using specific substrates to systematically vary both the heteroepitaxial strain (compressive vs. tensile) and growth orientation ((001) vs. (110)). Transmission electron microscopy, electron energy-loss spectroscopy, high-resolution X-ray diffraction, magnetometry, polarized neutron reflectometry, and electronic magnetotransport measurements are applied. Lattice mismatch and growth orientation are found to precisely control interfacial oxygen vacancy ordering in La1-xSrxCoO3-, thus dictating strain relaxation and chemical depth profiles, and in turn controlling thickness-dependent magnetic and electronic properties. In particular, compressive strain and (110) orientations are found to minimize deleterious magnetic/electronic dead layer effects, leading to optimization of interfacial magnetism and transport. Strain and orientation tuning of oxygen vacancy ordering are thus established as powerful means to control physical properties at cobaltite-based interfaces, of relevance to several fields.