Large uniaxial magnetic anisotropy of Co-Pt perpendicular films induced by lattice deformation

A study of the thickness dependence of the uniaxial magnetic anisotropy K-u of Co-Pt perpendicular films deposited on Ru seed layers was extended over a wide range of Pt content from 10 to 30 at%, to further investigate the origin of the significant increase in K-u on reducing the film thickness, which was previously reported for Co-80 Pt-20 /Ru films. K-u increased significantly as the thickness decreased in all series (if films with various Pt content. The rate of increase of K-u with reducing thickness became increasingly large as the Pt content decreased. It should be noted that the K-u of 2-nm-thick films was an almost constant 2 x 10(7) erg/cm(3) over the range of Pt contents studied, although K-u was maximized at 25-30at%Pt content for films thicker than 5 nm. Experimental results suggest that the increase in K-u on reducing the thickness was mostly related to a reduction of the hcp Co-Pt lattice c/a ratio.