Asymmetric wall structure observation by deflection pattern in transmission Lorentz microscopy

Deflection patterns of 180° domain walls in epitaxially grown iron films from 500 to 3000 Å in thickness were examined using an illumination angle of 8 × 10^-7radian, an effective size of selected area aperture of 2.2 μm in diameter, and different exposure times for each film thickness at an effective camera length of 10 m. In the deflection pattern, an asymmetric intensity distribution along the streak was observed. It was explained by an asymmetric magnetization distribution across the wall. In addition, the streak split into two or more parts in the films thicker than about 1300 Å. It was concluded to be due to an asymmetric magnetization distribution along the film thickness. Sense of both types of asymmetries changed alternately along a 180° wall. Such three dimensional wall structure is discussed to be caused by effects of grains of about 2000 Å.