Lorentz Microscopy of Recorded Magnetization Patterns

Abstract

We have used the technique of transmission electron microscopy for the static observation of recorded magnetization patterns in high‐coercivity films of cobalt and iron. Such magnetization patterns consist of a series of oppositely magnetized regions, and are characterized by the length of these magnetized regions and by the spatial variation of the magnetization in the transition regions in which the magnetization reverses from one direction to the opposite direction. Magnetic bit patterns of different wavelengths were recorded with conventional high‐resolution transducers and by magnetic transfer from high‐coercivity masters. The Foucault method using the objective aperture diaphragm was found particularly applicable for observing the oppositely magnetized regions, resulting in good contrast for wavelengths as small as 2 μ. For the observation of the magnetization transition regions, the defocus mode was found better applicable. Measurements of the length of the transition region by this method are in good agreement with our theoretical calculations using harmonic analysis to determine the resulting demagnetization.