Abstract
Magnetic proximity effect between two magnetic layers is an important focus of research for discovering new physical properties of magnetic systems. Antiferromagnets (AFMs) are fundamental systems with magnetic ordering and promising candidate materials in the emerging field of antiferromagnetic spintronics. However, the magnetic proximity effect between antiferromagnetic bilayers is rarely studied because detecting the spin orientation of AFMs is challenging. Using X-ray linear dichroism and magneto-optical Kerr effect measurements, we investigated antiferromagnetic proximity effects in epitaxial CoO/NiO/MgO(001) systems. We found the antiferromagnetic spin of the NiO underwent a spin reorientation transition from in-plane to out-of-plane with increasing NiO thickness, with the existence of vertical exchange spring spin alignment in thick NiO. More interestingly, the Néel temperature of the CoO layer was greatly enhanced by the adjacent NiO layer, with the extent of the enhancement closely dependent on the spin orientation of NiO layer. This phenomenon was attributed to different exchange coupling strengths at the AFM/AFM interface depending on the relative spin directions. Our results indicate a new route for modifying the spin configuration and ordering temperature of AFMs through the magnetic proximity effect near room temperature, which should further benefit the design of AFM spintronic devices.
Highlights
Contact between materials with different magnetic orderings can modify their properties near the interface owing to exchange coupling
Using the element-specific X-ray magnetic linear dichroism (XMLD) effect, we demonstrate that the AFM spin orientation of NiO changes from in-plane to out-of-plane with increasing NiO thickness, and the existence of a vertical exchange spring alignment in thick NiO
To investigate the magnetic properties of the CoO layer, CoO L3 edge spectra were measured with X-rays at normal incidence (θ = 0 ) and grazing incidence (θ = 70 or θ = 60 )
Summary
Contact between materials with different magnetic orderings can modify their properties near the interface owing to exchange coupling. This phenomenon is usually called magnetic proximity effect. Bulk NiO has a TN of ~523 K, and bulk CoO has a lower TN of ~293 K These distinct spin orientations and TNs enable us to study the AFM proximity effect on AFM spin orientation and TN in this system. Our results provide clear evidence that the magnetic proximity effect in AFM/AFM bilayers can influence the spin direction and ordering temperature within 2–3 nm of the interface, which is crucial for designing AFM spintronic devices
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