Interfacial Octahedral Rotation Mismatch Control of the Symmetry and Properties of SrRuO₃

Epitaxial strain can be used to tune the properties of complex oxides with perovskite structure. Beyond just lattice mismatch, the use of octahedral rotation mismatch at heterointerfaces could also provide an effective route to manipulate material properties. Here, we examine the evolution of the structural motif (i.e., lattice parameters, symmetry, and octahedral rotations) of SrRuO₃ films grown on substrates engineered to have the same lattice parameters, but different octahedral rotations. SrRuO₃ films grown on SrTiO₃ (001) (no octahedral rotations) and GdScO₃-buffered SrTiO₃ (001) (with octahedral rotations) substrates are found to exhibit monoclinic and tetragonal symmetry, respectively. Electrical transport and magnetic measurements reveal that the tetragonal films exhibit higher resistivity, lower magnetic Curie temperatures, and more isotropic magnetism as compared to those with monoclinic structure. Synchrotron-based quantification of the octahedral rotation network reveals that the tilting pattern in both film variants is the same (albeit with slightly different magnitudes of in-plane rotation angles). The abnormal rotation pattern observed in tetragonal SrRuO₃ indicates a possible decoupling between the internal octahedral rotation and lattice symmetry, which could provide new opportunities to engineer thin-film structure and properties.