STEM of order and dynamics in novel magnetic materials
The new detection system of the HB5 STEM enables the operation of the microscope in a variety of modes. If the specimen is placed inside the objective lens, high resolution bright and dark field images revealing the microstructure can be obtained. Since the specimen is located in a high magnetic field, magnetic ordering phenomena are disturbed and no magnetic structure contrast is observed. In the out-of-field position, magnetic structure may be revealed in the Fresnel and Differential Phase Contrast modes of Lorentz Microscopy. Fresnel images are obtained with a static beam, i.e. the scanning coils are not excited. In the Fresnel mode the objective lens focus is changed slightly and domain walls appear in the shadow image as dark and bright lines, switching contrast when the objective lens is changed between overfocussing and underfocussing. Electrons, passing through the sample, are deflected by the Lorentz force and appear to converge towards or diverge from the domain walls.