A new pathway to correlate the octahedral tilt coupling and spin-orbit reconstruction at oxide interfaces

Abstract The direct experimental probing and detailed imaging of octahedral tilt, along with the control of magnetic ground state and spin-orbit occupancies in an artificially engineered heterointerface through the manipulation of strain via interface engineering, is the long-standing challenging issue addressed in this study. We introduce a novel methodology that involves the measurement of the projected O-O-O angles (OOOproj) between the neighboring in-plane BO6 octahedra of perovskite oxide (ABO3), demonstrating a precise quantification of strain-manipulated octahedral tilt in atomically engineered La0.7Sr0.3MnO3 (LSMO)/LaCoO3 (LCO) bilayer interfaces. The pronounced octahedral tilt on SrTiO3 (STO) substrate (under tensile strain) compared to LaAlO3 (LAO) substrate (under compressive strain) correlates with the enhanced (suppressed) magnetism under tensile (compressive) strain in bilayer configuration, especially within the framework of bond angle geometry and spin-charge-orbital reconstructions, contrasting with strain effects reported on individual single-phase films. Interfacial orbital reconstruction, Co/Mn antiferromagnetic coupling and their manipulation under strain are quantified through X-ray linear dichroism (XLD) and X-ray magnetic circular dichroism (XMCD) measurements, further confirmed by both molecular orbital theory and Goodenough-Kanamori-Anderson rules. First principles calculations unveil a higher (lower) magnetic moment of individual magnetic atoms with tensile (compressive) strain, while also explaining the unusual interfacial antiferromagnetism arising from the interplay of out-of-plane and in-plane d-orbital occupations, and the role of bond angle geometry. This endeavor paves a potential method to manipulate the octahedral tilt and resultant perturbed crystal field energy to explore and tailor emergent phenomena at heterointerfaces via atomically precise strain-interface engineering.