Fabrication of isolated magnetic nanostructures by using nanoporous anodic alumina films on Si

Arrays of magnetic Ni nanostructures have been fabricated on a Si substrate by using a nanoporous alumina film as a mask during the deposition. The nanostructures have a truncated cone shape, and the lateral sizes are comparable to the heights. While a continuous film shows well-defined in-plane magnetization, the nanostructure has a perpendicular component of the magnetization at remanence. The hysteretic behavior of the nanostructures is dominated by the demagnetizing field instead of by interaction among the structures.