Magnetic and Magneto-Optic Properties in Compositionally Modulated TbCo Films

The magneto-optical and magnetic properties of compositionally modulated TbCo films were studied. Films were prepared on glass substrates by rf sputtering, using a modulating substrate bias voltage in one of the two sequences, -200 V/0 V/..../0 V or -250 V/0 V/..../0 V. Single-layer films deposited at 0 V have a high perpendicular magnetic anisotropy K_u, a small Kerr rotation angle θ_K and good chemical stability; while films formed under a high bias have a low K_u, large θ_K and poor chemical stability. The period of modulation was varied between 1500 Å and 40 Å, and Rutherford backscattering spectrometry and small-angle X-ray scattering were used to confirm that films actually were compositionally modulated with these periods. The modulated films showed a higher K_u and greater resistance to oxidation. A high θ_K and high reflectivity on the glass substrate side can be obtained with such a multi-layered structure.