Interplay of magnetic proximity effect and epitaxial strain in transition metal monoxide antiferromagnetic...

Controlling magnetic order in antiferromagnetic (AFM) materials is crucial for advancing spintronic technologies. Although epitaxial strain and magnetic proximity effects are known to independently influence AFM properties, their combined interplay in all-antiferromagnetic heterostructures remains largely underexplored. Here, we employ element-specific X-ray magnetic linear dichroism (XMLD) spectroscopy to investigate how epitaxial strain and interfacial exchange coupling cooperatively tune magnetic ordering temperatures and spin orientations in MnO/NiO/CoO heterostructures grown on MgO(001) substrates. We demonstrate that magnetic proximity effects dramatically enhance the Néel temperature of ultrathin MnO when grown on CoO and NiO, showcasing the significant impact of interfacial exchange coupling. Through a systematic comparison of experimental and simulated angular-dependent XMLD measurements, we reveal that the NiO spin orientation is strongly governed by strain: the epitaxial tensile strain from MgO(001) stabilizes the out-of-plane alignment, while the compressive strain of the Cr buffer layers enforces the in-plane configuration. Remarkably, magnetic proximity to CoO overrides strain effects, imposing in-plane anisotropy within the NiO layer. In MnO/NiO bilayers, we observe bidirectional magnetic proximity effects, where out-of-plane-oriented NiO spins induce partial out-of-plane canting in MnO, while MnO simultaneously drives partial in-plane rotation of NiO spins. Our results establish that rational design of all-AFM heterostructures enables systematic control of antiferromagnetic order through the interplay of epitaxial strain and magnetic proximity, providing a versatile route for engineering spin configurations in AFM-based spintronic devices.