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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 Neel 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.
