Electron holography and magnetic specimens

Electron holography and electron interferometry for magnetic specimens have no close analogy to counterparts in visible-ray optics, while there are such counterparts for nonmagnetic specimens. Formulas are presented for the relation between the magnetic structure of specimens and the phase information that can be determined using such techniques. Some simulation examples using the formulas are demonstrated including a display of the Aharonov-Bohm effect in a form of interferometry. In addition, how a magnetic monopole should appear on an electron hologram and how its strength and sign should be determined from the hologram are illustrated. The interference fringes on the hologram must look like "a dislocation in a set of parallel lines." The number of extra lines corresponds to the strength of the monopole.