Growth induced magnetic anisotropy in Co-doped garnet and its capability of application to magneto-optical memory materials

Growth-induced magnetic anisotropy (Kug) normal to the film surface in Co-doped iron garnet films grown on GGG substrates by the LPE method has been quantitatively discussed. Kug is increased with increasing Co content and growth rate (Vg). From the measurement of temperature dependence of magnetocrystalline anisotropy K
1
, the parameter αλ is evaluated to be 80 cm
^-1
through a curve fitting procedure using Slonczewski's theory of Co single-ion model for the anisotropy. After the annealing at temperatures above 900°C, Kug is disappeared and K
1
is increased: These changes are successfully interpreted by the theory using the above value αλ. Also shown is the magnetic field effect on the perpendicular anisotropy of poly-crystalline Co-doped BiDyGeIG films prepared by the pyrolysis method on glass substrates for the purpose of application to magneto-optical memory materials. In these films, (Ge(CH
2
)
2
COOH)
2
O
3
is found to be a suitable solute for adding tetravalent Ge ions. In this method, an increase of Co amount raises the crystallization temperature, while doping of Ge lowers it. A magnetic field perpendicularly applied to the film during the heat treatment for crystallization enhances the anisotropy, whereby Ku is increased to about 170% of those of films prepared with no field.