Effect of magnetic field on the electrodeposition of Fe, Co into the pores of anodic film on aluminum

Ferromagnetic Fe or Co was electrodeposited into the pores in aluminum anodic oxide film to produce a magnetic anodic film, and the effects of magnetic field during electrodeposition on the deposition characteristics of the metals and coercivity of the produced anodic film were investigated. Fe was electrodeposited into the pores in anodic film using a mixed solution (pH=3.8) of FeSO4(NH4)SO4.6H2O (0.20 mol/l) and H3BO4 (0.48 mol/l) at 20 °C with constant applied voltage of 10 V, and Co using a mixed solution (pH=4.5) of CoSO4,7H2O (0.10 mol/l) and H3BO4 (0.48 mol/l). It has been found that for the Fe-deposited anodic film the coercivity increased with increasing length of deposited Fe particles and decreased with increasing diameter (or porosity). The application of magnetic field during electrodeposition of Fe had little influence on the coercivity of the anodic film. For the Co-deposited anodic film the coercivity increased with increasing length of deposited Fe particles and increased unexpectedly with increasing diameter. The perpendicular coercivity of the Co-deposited anodic film was significantly increased by the application of magnetic field during the electrodeposition. The unexpected coercivity increase with diameter and the increase of the perpendicular coercivity of Co-deposited film by the application of magnetic field were closely related to the preferred orientation of Co crystals in the anodic film.