Strain–induced robust ferromagnetism and exchange bias effect in epitaxial LaMnO3/SrFeO2.5 bilayer

Abstract

Exchange bias (EB), commonly observed at the interface between ferromagnetic (FM) and antiferromagnetic (AFM) materials, significantly impacts the performance of magnetic memory devices. Here, we employed A–type AFM LaMnO₃ (LMO) and G–type AFM SrFeO_2.5 (SFO) native materials as the research subjects, and constructed bilayers with reversed stacking sequences. When SFO was deposited preferentially, the ferromagnetism and EB effect of the SFO/LMO bilayer were relatively weak. Conversely, when LMO was deposited preferentially, the large tensile–strain provided by the SrTiO₃ (STO) substrate led to an increased presence of Mn⁴⁺ ions within the LMO layer in the LMO/SFO bilayer, in which the double exchange mechanism of the Mn³⁺–O–Mn⁴⁺ ions not only resulted in robust ferromagnetism but also coupled with SFO to generate a significant EB effect. Our research presents a strategy for modulating the magnetic properties and the coupling behavior at the heterogeneous interface via strain engineering, thus broadening the techniques for generating EB.