Magnetic and crystallographic study of Co electrodeposited alumite films

Magnetic properties and crystallographic structures of alumite films of which pores were filled with Co were investigated. The perpendicular magnetic anisotropy energy of the films was smaller than their shape anisotropy energy, which is due to the magnetocrystalline anisotropy of hcp-Co particles in the pores. The c-axis orientation of hcp-Co particles was found to be influenced by the pH near the cathode and the ac frequency used in the deposition. The c axis rose from the in-plane direction of the film to the normal one when the Co was electrodeposited into the pores at high pH value and low ac frequency, and the perpendicular magnetic anisotropy of the films increased. The deposition of Co at high pH value and low ac frequency was supposed to decrease the current density in the reduction process of Co²⁺ ions, which caused the preferred c-axis orientation to the normal direction of the film.