Controllable magnetic anisotropy and magnetostriction constant in palladium cobalt alloy films: Effects of composition, thickness, and stress

The magnetic anisotropy of sputter-deposited films of palladium cobalt Pd100 − xCox (x = 7, 15, and 28 at. %) alloy is investigated systematically. The exact anisotropy energies of all contributions, namely, surface, magnetocrystalline, magnetoelastic, and shape, are estimated. Using these energies, the main origin of the magnetic anisotropy is determined and summarized in maps of film thickness and film stress. Consequently, how composition, thickness, and stress affect the magnetic anisotropy is clarified. Accordingly, the controllability between longitudinal and perpendicular magnetic anisotropy is revealed. In addition, the magnetostriction constant λ111 is estimated from the change in the volume anisotropy energy due to the stress in the film, namely, the inverse magnetostrictive effect. The constant is a large negative number, −178 ppm at maximum, and agrees partially with a reference value measured under normal magnetostriction. The disagreement by 30% of the magnetostriction constant with respect to the expected value for Pd72Co28 films was elucidated by the magnetostriction enlargement by tensile stress.