Well-aligned Ni and Co-NiO-Ni core-shell nanotube arrays with an average outer diameter of about 200 nm have been synthesized in a porous anodic aluminum oxide (AAO) template by the direct electro-deposition method. The result shows that the nanotubes were polycrystalline phase. Angular dependent coercivity H c indicates that the magnetization reversal mechanisms are mainly dominated by the curling mode for Ni nanotubes, while a transition from curling to transverse is observed in Co-NiO-Ni core-shell nanotubes at a large angle. A sharp increase in saturated magnetization (M s) of Ni and Co-NiO-Ni core-shell nanotubes at 5 K was observed, due to dominance of the surface effect. Besides, the existed superparamagnetic nanoparticles also resulted in the increase of M s for both cases. These structures have potential applications in the novel spintronics device, ultrasmall magnetic media, and other nanodevices.
Bibliographical noteFunding Information:
The project was supported by the State Key Project of Fundamental Research of Ministry of Science and Technology (MOST, No. 2010CB934400) and National Natural Science Foundation of China (NSFC, Grant Nos. 10934099, 10874225, and 51021061), and the partial support of Graduate Education Project of Beijing Municipal Commission of Education, the international joint projects of NSFC-The Royal Society (UK) and the partial support of K. C. Wong Education Foundation, Hong Kong.