A study of cross-tie domain walls in cobalt using small-aperture Foucault imaging

Abstract Two types of cross-tie domain wall seen in a cobalt film have been studied by Foucault imaging in the transmission electron microscope. The images are taken with a contrast-forming aperture that subtends a smaller angle than the angular deflections of the electron beam introduced by the magnetization in the sample. The small-aperture Foucault technique is implemented using lens settings that produce high magnification diffraction patterns and a television camera is used to improve the limited image magnifications that are associated with this operating mode. With a small aperture the magnetic induction vector can be assigned with greater accuracy to the bright regions in the Foucault image, and the real-space origins of diffraction features are easy to identify. For the two different types of cross-tie domain wall maps of the magnetic induction are constructed from a series of Foucault images, and diffraction streaks are identified as originating from the domain wall.