Radially distributed Ni and Co nanowire arrays

Abstract

Ni and Co nanowire arrays are prepared by electroplating filling of self-assembled radial nanopores in cylindrical anodic alumina, and their magnetic behavior is compared with that of nanowire arrays with the same geometry parameters in a planar configuration. Diameter and length of radially oriented nanowires are 35nm and 2μm, respectively. They are arranged in hexagonal symmetry with lattice constant of 105nm within a 5μm thick porous microtubular alumina shell with an outer diameter of 100μm. The magnetic response of such arrays has been investigated for magnetic field applied along parallel and perpendicular directions. The azimuthal distribution of radial nanowires in the cylindrical configuration grants a different magnetic response in comparison with that of arrays in conventional planar configuration. The study of hysteresis loops reveals a clear radial anisotropy for Ni nanowire arrays owing to the shape anisotropy of individual nanowires. However, for Co nanowire arrays a nearly isotropic behavior is observed, which is ascribed to the near balance between circular magnetocrystalline anisotropy and radial shape anisotropy of individual nanowires.