Strain-Controlled Atomic Scale Distortions and Anti-Ferromagnetism at LaFeO3/SrTiO3 Interface

Antiferromagnetic insulators have gained attention due to low loss, fast switching, and potential for next-generation spintronics applications. To achieve this, understanding the process of switching and control of magnetic properties via external stimuli, such as strain and applied fields, needs to be established. We report notable changes in magnetic canting in antiferromagnet LaFeO₃ thin films grown on SrTiO₃, which originates from the changes in the lattice distortion at the interface. Atomic-scale scanning transmission electron microscopy (STEM) reveals that the rotation of Fe-O octahedra changes within the first ~ 5 orthorhombic unit cells, with both the in-plane and out-of-plane rotations, progressively decreasing near the interface. Cation (La) positions are also affected by the strain at the interface, showing less distortion due to the connection to the cubic SrTiO₃. Nanoscale structural domains were also observed, and they are connected to the formation of magnetic domains near the interface, which we directly image using Lorentz TEM. Based on the experimental results, density functional theory calculation is performed to help elucidate the exact mechanism of the observed structure-property relationship.