Perpendicular Magnetic Anisotropy of TbFe, TbFeCo, and Dy-Fe Compositionally Modulated Films

Compositionally modulated TbFe and TbFeCo amorphous films were prepared on glass substrates by the bias-modulated sputtering method. The modulated structure was confirmed for modulation lengths larger than 14 Ã… by X-ray small angle diffraction. Sharp layer boundaries were clearly observed using cross-sectional TEM. The magnetic perpendicular anisotropy energy Ku increases with decreasing modulation length ¿, because of the interface anisotropy Ks which arises from the anisotropic ordering of Tb-Fe atom pairs or the internal stress at the layer boundaries. Dy-Fe multilayered films prepared by a vacuum evaporation technique were also investigated. As the periodic length ¿ decreases, both the saturation magnetization Ms and the Kerr rotation angle ¿K decrease sharply near ¿ ¿ 40Ã… because of the change in the Fe crystal structure from bcc to fcc or amorphous. The perpendicular anisotropy ku increases proportionally to 1/¿, with an interface anisotropy kS = 0.8 erg/cm² and kS = 1.24 erg/cm² at room temperature and at 80°K, respectively.