Magnetic properties and phase composition of the thin layers of Co-Pd system

One of the most important areas of space material science and metallurgy is studying phase and structural transitions of the metallic systems and alloys in connection with their magnetic properties. It advances the fundamental science but also leads to producing materials of desired complex magnetic structure. This paper deals with preparation and study of the Co-Pd thin films of various stoichiometry, obtained at different substrate temperatures and regimes. We examined phase composition, crystalline structure and its variation, saturation magnetization, coercive force, magnetic crystallographic anisotropy, exchange interaction parameter, perpendicular magnetic anisotropy constant of the films made. The properties of the systems were studied in connection with the conditions and regimes of the film preparation. The results reveal a number of metastable states which are absent in the bulk samples of the same overall composition. The saturation magnetization behavior implies a magnetic interactions interplay which affects the exchange interaction. Magnetic crystalographic anisotropy constant of the films changes with the temperature so that rich-Pd samples appear to be mostly zone ferromagnetic. We suggest a theoretical model of two-phase Co-Pd system (with fcc and hcp regions). The calculated value of the torque acting upon the film is in agreement with the experiment. The model explains the effect of the easy magnetization axis becoming perpendicular to the film/substrate plane, which is the case for films with 0.5-0.55 palladium content. This unusual property favours the possible use of the materials for high density data recording.