IMPROVED FOUCAULT IMAGING OF MAGNETIC DOMAINS WITH A MODIFIED 400 KV TRANSMISSION ELECTRON-MICROSCOPE

Modifications have been made to a 400 kV side-entry transmission electron microscope fitted with a low-field objective pole piece, in order to position apertures close to the back focal Plane of the objective lens, as there is no direct access to the required position in the column. The modifications have facilitated developments in the imaging of magnetic domain structure in magnetic materials using the Foucault technique, for which the correct positioning of the objective aperture is crucial. All usual transmission electron microscopy facilities are retained, allowing a full range of specimen holders and imaging modes to be used along with TV recording and electron energy loss spectroscopy. Some initial results are presented from Fe/Cr and Co/Pt multilayer films, for which the Lorentz deflection angle is very small, and for which the Fresnel imaging mode is of limited use as the grain structure contrast masks the magnetic contrast. Initial results are also presented from NdFeB permanent magnet material for which the use of a high electron accelerating voltage is necessary.