Strain Control of Structure and Emergent Magnetism in LaCoO3 Thin Films

Strain engineering in epitaxial LaCoO₃ thin films enables direct control of crystal symmetry and spin state population, revealing a clear pathway from lattice distortion to emergent magnetism in correlated oxides

• Demonstrated that tensile strain (SrTiO₃ substrate) stabilizes an orthorhombic Imma structure with a^-a^-c⁰ octahedral tilting, breaking bulk rhombohedral symmetry

• Showed that strain modifies Co-O bond lengths and angles, altering crystal field splitting and stabilizing a mixed spin state of Co³⁺ ions

• Established emergence of ferromagnetism (T_c ≈ 63-70 K, M_sat ≈ 0.3 μB/Co) in stoichiometric films without oxygen vacancies, isolating intrinsic strain effects

• Confirmed uniform magnetization independent of thickness, ruling out interface or defect driven magnetism