Fabrication of epitaxial fcc Co/Cu nanostructures/Si(001)

Isolated epitaxial Co(5 nm ≤ t_Co ≤ 30 nm)/Cu nanostructures have been fabricated on a Si(001) substrate by using a nanoporous anodic aluminum-oxide (AAO) film as a mask during evaporation. The structural and the magnetic properties of the nanostructures are compared with those of as-grown films. The results of X-ray diffraction confirm that both the film and the nanostructure have a fee structure with a (001) surface and a Co[110]//Cu[110]//Si[001] crystallographic relation in the plane. The nanostructures with t_Co ≥ 10 nm show clear four-fold symmetry of the remanent magnetization in the plane, but due to dipole interactions among nanodots, their values are smaller than those of films. The nanostructure with t_Co = 5 nm shows isotropic hysteresis loops while the film with the same thickness shows a four-fold symmetry.