Substrate-surface-structure tuned electrical and magnetic properties of PrCoO3/CaCoO2.5 superlattices

Abstract

Interface engineering using substrate surface structures, especially the surface steps, terraces, and facets, is an effective way of tuning the physical properties of epitaxial films and superstructures. The superlattices comprising perovskite PrCoO₃ and brownmillerite CaCoO_2.5 were grown on three different surface structures, namely, the (001) SrTiO₃ substrate with clear surface-step-terraces, the (001) (LaAlO₃)_0.3(Sr₂AlTaO₆)_0.7 (LSAT) substrate with poorly defined surface-step-terraces, and the (001) LaAlO₃ substrate with zig-zag surface facets. The superlattices on LaAlO₃ substrates not only exhibit superior ferromagnetic properties but also greater electrical conductivity, with their room-temperature resistivities at the most four orders of magnitude smaller than those on SrTiO₃ and LSAT substrates. The antiphase domain boundaries that extend all the way from the interface to the surface can be formed at the edges of the surface-step-terraces, which impede the pathways for charge carrier hopping and magnetic exchange interactions, thereby leading to the well-disciplined ferromagnetic insulating properties of the superlattices on SrTiO₃ and LSAT substrates. These results provide new insights into the understanding of the correlation between substrate surface structures and physical properties of the superlattice system.