Facile preparation and magnetic properties of Ni nanotubes in polycarbonate ion-track templates

Ni nanotubes, with an inner diameter of about 100 nm and different wall thicknesses (approximately 20, 50, 80 and 110 nm), were successfully fabricated in porous polycarbonate (PC) ion-track templates by a novel method including two-step ion-track etching, two-step electrochemical deposition and one-step electrolysis. In our experiment, wall thickness of Ni nanotubes can be effectively controlled through the etching time of templates. The morphologies and crystal structures of the nanotubes were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The magnetic hysteresis loops measured via vibrating sample magnetometry (VSM) indicate that Ni nanotubes with thinner wall thickness possess larger squareness and coercivity value when magnetic field applied parallel to the nanotube׳s axis, which can be attributed to the shape anisotropy and the formation of multi-domain structure.