Flux-line observation by electron Holography

In electron microscopy, the intensity of an electron beam transmitted through an object can be observed. While in electron holography, the phase of the electron beam can also be observed and displayed as an interference micrograph. Using a technique unique to holography, the precision of phase measurements can be increased to 1/100 of the electron wavelength. An interference micrograph of a magnetic object can be interpreted in a straightforward way: Contour fringes directly indicate projected magnetic flux lines and a constant magnetic flux of h/e (= 4 × 10-15 Wb) flows between two adjacent fringes (See Fig. 1).Examples of magnetic recordings are shown in Fig. 2. Flux lines inside and outside of the magnetic tapes, recorded in different ways, can directly and quantitatively be observed as interference micrographs. Figure 2 (a) shows an example of in-plane magnetic recording. Two magnetization streams, pointed in opposite directions, merge and produce vortices in the transition region similar to those produced by streams of water.