Exchange bias coupling in NiO/Ni bilayer tubular nanostructures synthetized by electrodeposition and thermal oxidation

•NiO-Ni bilayer tubular nanotubes were fabricated by electrodeposition and thermal oxidation.•The exchange bias effect in NiO-Ni nanotubes was induced by magnetic field cooling.•The competitive effect of annealing temperature and annealing time on the exchange bias coupling was analyzed.

In this paper, we reported the synthesis of NiO/Ni bilayer nanotubes by electrodeposition and thermal oxidation using anodic aluminum oxide templates. The morphology, structure, chemical composition and magnetic properties, especially magnetic exchange bias induced by subsequent magnetic field cooling, in this one-dimensional antiferromagnetic/ferromagnetic hybrid system were investigated. It was found that the effect of the annealing temperature, which mainly dominated the thickness of the NiO layer, and the annealing time, which mainly dominated the grain size of the NiO, on the exchange bias field showed competitive relationship. The optimized exchange bias field was achieved by the combination of the shorter annealing time and higher annealing temperature.