An unconventional pathway to correlate the octahedral tilt coupling and spin-orbit reconstruction at oxide interfaces

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 strain manipulation via interface engineering, is the long-standing challenging issue addressed here. We introduce an innovative methodology to measure the projected O-O-O angles (O-O-O_proj) between the neighboring in-plane BO₆ octahedra of perovskite oxide (ABO₃), demonstrating a precise quantification of strain-manipulated octahedral tilt in atomically engineered LaCoO₃ (LCO)/La_0.7Sr_0.3MnO₃ (LSMO) bilayer interfaces. The pronounced octahedral tilt on SrTiO₃ (STO) substrate (tensile strain) compared to LaAlO₃ (LAO) substrate (compressive strain) correlates to the magnetism especially within the framework of bond angle geometry and spin-charge-orbital reconstructions, contrasting with individual single-phase films. Interfacial orbital reconstruction, Co/Mn antiferromagnetic coupling and their strain manipulation 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, including unusual interfacial antiferromagnetism arising d-orbital occupations, and bond angle geometry. This endeavor paves a potential method to manipulate the octahedral tilt to tailor emergent phenomena at heterointerfaces via atomically precise strain-interface engineering.