Magnetic Anisotropy of Suppttered Co-Cr Thin Films

Co-Cr and Co-Cr-W films were prepared by DC magnetron sputtering on PET film. The dependence of the magnetic anisotropy constants Ku1 and Ku2 on the film thickness was determined from torque curve measurements. When the film thickness is thin, the Ku1 is very small, and it increases rapidly as the film thickness increases. On the other hand, the Ku2 is extremely large for thin films, but drops rapidly with increasing film thickness, approaching a nearly constant value. The ratio Ku1/Ku2 is not constant. The dependences of ¿2 and ¿4, the tilt angles of the easy magnetization axis from the film normal for Ku1 and Ku2, on the film thickness were measured. The value of ¿2 was not equal to that of ¿4. These results suggest that there is another fourfold symmetry besides that of the uniaxial anisotropy.