Synthesis and magnetic properties of Ni nanocylinders in self-aligned and randomly disordered grown titania nanotubes

A novel ferromagnetic/semiconductor oxide nanocomposite formed by arrays of Ni nanocylinders grown by the electrodeposition technique in a semiconductor oxide matrix of self-aligned and randomly disordered titanium dioxide nanotubes has been synthesized. X-ray diffraction, EDX, SEM, AFM, rf-GDOES and VSM magnetometry techniques have been used to investigate the structural, compositional and morphological properties, as well as its specific magnetic behaviour. Titania nanotubes have been grown through a single anodization process, by using HF acidic electrolytes in a potentiostatic mode. The thus-obtained titanium dioxide nanotube outer diameter ranges between 90 and 150 nm, wall thickness about 25–40 nm and 300 nm in depth. The electrodeposited Ni nanocylinders reach above 100 nm diameter and 240 nm length, giving rise to coercive fields of 98 and 200 Oe, well within the hysteresis loops perpendicular or parallel to the nanocylinder axis, respectively, which could be ascribed to the formation of magnetic vortex domain states. It is expected that this novelty nanocomposite, based on ferromagnetic Ni nanocylinders embedded in a semiconductor titanium dioxide nanotube template, will become a promising candidate for many applications in a broad range of scientific and technological areas, such as ultrahigh density magnetic storage media or spin-based electronic devices.