| 摘要 |
A method and an apparatus for characterizing magnetic materials especially LPE garnet films for magnetic bubble memory applications are described. The method and apparatus comprises in the first embodiment passing monochromatic linearly polarized light through a magnetic film, under no applied external field (Ha=0) with a randomly oriented stripe domain structure to produce a single diffraction grating, then (1) the angle of the first order diffracted beam is deduced by directly comparing the currents produced by a linear position photodetector and an ordinary intensity photodetector and (2) next a magnetic field (Ha) is applied normal to the surface of the film and the field is increased until intensity of the second order diffraction beam is maximized. In the second embodiment of the method so that higher signals can be detected for the first order diffracted beam, the film is magnetized so that the stripe domain configuration is parallel and the foregoing steps followed. The angle of the first order diffracted beam relates to the stripe width of the magnetic film under no applied external magnetic field. The magnetic field which corresponds to the intensity maximum of the second order diffracted beam is the field, H0.5, which magnetizes the film to M=0.5xMs, where M is the net magnetization of the film and Ms is the saturation magnetization. The stripe width at Ha=0 and the field H0.5 determine the diameter of the magnetic bubble domain that the film will support and the magnetic field necessary for bubble collapse. The apparatus for carrying out the foregoing method is all solid state and needs no mechanical feedback or mechanical adjustments.
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