Induced magnetic anisotropy of Co-P thin films obtained by electroless deposition

Co1−x-Px films (x = 0.02–0.05) deposited on cover glass by electroless plating from aqueous solutions in a continuous magnetic field with the strength of 2.5 kOe are presented. It has been found that in the pH range from 7.2 to 9.3, two special areas can be distinguished, they are characterized by the deposition of films with qualitatively different parameters in them. So, the change of the pH of working solutions from 7.2 to 8.7 causes the increase in the value of the induced magnetic anisotropy constant KU from 2.5 × 105 erg/cm3 to 6 × 105 erg/cm3. If the value of the hydrogen index is still increasing, an uneven drop to 5 × 104 erg/cm3 is observed. In the same way, the coercivity HC changes; at first it grows from 700 Oe to 1.5 kOe, and then it drops to Oe units. The concentration of phosphorus in the range of 7.2 to 8.7 increases linearly from 2 to 3 wt%, and in the range of 8.7 to 9.3, it increases from 3 to 5 wt%. The x-ray diffraction data show that the samples obtained at pH < 8.7 are characterized by the presence of the hcp phase of Co (α-Co). The observed reflections of films obtained at pH > 8.7 indicate the fcc-Co (β-Co) with the diffraction peak blurring: the greater the pH value of the samples obtained, the more the diffraction peak blurring. It is shown that the induced magnetic anisotropy in high-coercivity films relates to the modification of the Co lattice. The lattice passes from a distorted fcc to an hcp structure during the growth of crystallites in a magnetic field. The induced magnetic anisotropy appears in films that were obtained in the high pH field due to the ordering of magnetic ions pairs.