Interfacial structure, evolution and magnetic properties of NiO/Cr₂O₃ heterostructures

Interfacial structure and its evolution play an important role in determining the functional properties of advanced materials and devices. However, real oxide heterointerfaces are typically far more complex than idealized abrupt boundaries; thus clarifying how interfacial structures evolve and how such evolution affects physical properties is essential. In this work, NiO/Cr₂O₃ heterostructures were epitaxially grown on single-crystalline SrTiO₃ substrates by pulsed laser deposition under different deposition temperatures and subsequent post-annealing treatment, both of which strongly influence the thermally driven interfacial evolution. Interfacial structures were comprehensively characterized by high-resolution X-ray diffraction and transmission electron microscopy equipped with energy-dispersive X-ray spectroscopy. The evolution is revealed as a transition from an ultrathin interfacial transition zone in the as-deposited NiO/Cr₂O₃ heterostructure to the formation of a NiCr₂O₄ reaction interlayer, and finally to a NiO/NiCr₂O₄ bilayer after high-temperature annealing. Magnetic hysteresis loops measured by a superconducting quantum interference device reveal that all heterostructures exhibit weak ferrimagnetism, accompanied by a non-monotonic change in saturation magnetization with interfacial structural changes. These findings demonstrate that thermally controlled interfacial reactions and structural evolution can generate distinct magnetic characteristics, thereby providing a practical strategy for material interfaces design and performance engineering in functional oxides.