Bi-Substituted DyIG Thin Films Prepared by Thermal Decomposition Method for Magneto-Optic Recording Medium

Highly Bi-substituted DyIG thin films on glass substrates with perpendicular anisotropy, which are candidates for use in magneto-optical recording, have been prepared by a thermal decomposition method. Nitrate solutions were spin-coated on glass substrates, and the resulting films were crystallized by annealing at temperatures between 560 and 660°C. X-ray diffraction studies verified that films were single-phase polycrystalline garnets. Dy substitution resulted in uniaxial anisotropy energies (K_u) of as high as 8 × 10⁴ erg/cm³. Compositional dependences of the saturation magnetostriction constant were measured using the cantilever method. Comparison of the measured and calculated anisotropies revealed that the large K_u values of Dy-substituted films originates in magnetostriction and internal stress. In static recording experiments, written bits about 1.5 μm in diameter were obtained. The Faraday rotation coefficient was 3. 7 deg/μm at a wavelength of 633 nm when the film Bi content was 1.55/formula unit.