Strain-Induced Robust Exchange Bias Effect in Epitaxial La_0.7Sr_0.3MnO₃/LaFeO₃ Bilayers

The ground state of correlated electrons in complex oxide films can be controlled by applying epitaxial strain, offering the potential to produce unexpected phenomena applicable to modern spintronic devices. In this study, we demonstrate that substrate-induced strain strongly affects the coupling mode of interfacial magnetic moments in a ferromagnetic (FM)/antiferromagnetic (AFM) system. In an epitaxial bilayer comprising AFM LaFeO₃ (LFO) and FM La_0.7Sr_0.3MnO₃ (LSMO), samples grown on a LaAlO₃ (LAO) substrate exhibit a larger exchange bias field than those grown on a SrTiO₃ substrate. Our results indicate a transition in the alignment of magnetic moments from perpendicular to collinear due to the large compressive strain exerted by the LAO substrate. Collinear magnetic moments at the LSMO/LFO interface generate strong exchange coupling, leading to a considerable exchange bias effect. Thus, our findings provide a method for tailoring and manipulating the orientations of magnetic moments at the FM/AFM heterogeneous interface using strain engineering, thereby augmenting methods for exchange bias generation.