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The properties of cylindrical domains in wafers of bulk single crystals of various magnetic oxides have been extensively studied and described in recent months. Mobile cylindrical domains have been produced in single-crystal thin films of gallium-substituted yttrium iron garnet. The deposits are formed by chemical vapor deposition onto nonmagnetic garnet substrates greater than 1 cm2 in area. A model of magnetic anisotropy in epitaxial films is proposed and shown to be in good agreement with experimental domain observations. In a typical sample, a domain diameter of 8 μ is observed in a 6-μ-thick film at a bias field of 25 Oe. From the domain translational velocity of 5600 cm/sec, a cylindrical domain mobility of 1500 cm/sec Oe has been calculated. A fractional change in cylindrical domain diameter of −0.07%/°K has been measured at 300°K. Annealing at 1570°K for several hours did not alter the Néel temperature or the optical transmission spectrum.

The chemical vapor deposition technique provides a means of growing single-crystal films of ferrite and garnet magnetic oxides on nonmagnetic substrates. The technique involves a chemical reaction at elevated temperatures between volatile metallic compounds and gaseous oxidizing agents on the substrate surface to form the solid film. It is possible to control the orientation of the magnetic vector with respect to the film, the film composition, and the surface condition of the film. The factors which affect the achievement of epitaxy and the crystal quality of the film include the structural similarity between the substrate crystal and the film, the chemical conditions of the reaction, the deposition temperature, the rate of crystal growth, and the relative expansion characteristics of the film and substrate. Epitaxial deposits of a variety of ferrites have been made on MgO, Al2O3, and MgAl2O3 single-crystal substrates in the deposition temperature range of 800° to 1100°C. Film thicknesses in the range 0.5 to 500 μ have been produced in (100), (110), and (111) orientations. The values obtained for saturation magnetization anisotropy constant and resonant linewidths are similar to bulk-crystal values of the same composition.

Large, thin-film single domain areas have been observed, in the absence of a bias field, in garnets with magnetization perpendicular to the film plane.1,2 The domain stability in the work by Krumme1 was attributed to a combination of low saturation magnetization and a low Curie temperature. Uchishiba2 relates the stability in his double layer system to appropriate anisotropy fields in one layer compared to the magnetization in the other layer. A more complete model for large domain stability in a bias field free environment is given in this work. Three distinct stability regimes are predicted by the model and all have been observed experimentally. Areas 3.5-cm in diameter have been made into stable single domains. This was achieved in a material showing a zero bias strip width of 4.5 μm. The single domain diameter was, therefore, 7500 times the equilibrium energy domain width. The technique developed and the model have led to a new means for observing magnetic defects. More importantly, it also offers a means for measuring the strength of the defects. Possible applications of the model are also discussed.

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