Electron Mirror Microscopy of Magnetic Domains

Electron mirror microscopy is a rather novel research instrument. It has recently been demonstrated that it can provide micrographs not only of the relief structure of a specimen but also of such purely electrical properties as contact potentials, conductivities, surface charges, and even space charges. This paper deals with the feasibility of electron mirror microscopy for pictorial representation of magnetic properties in general, and of magnetic domain patterns in particular. It is shown that electron mirror microscopy is actually a feasible and independent method for electronically depicting magnetic patterns. The section of the paper dealing with experimental work begins with magnetic specimens of artificial nature, e.g., a recorder head, containing one or more linear magnetic dipole stray fields which are controllable. After establishing the basic facts of magnetic contrast formation with this type specimen, the paper reports on experiments conducted with specimens of barium ferrite and nickel ferrite containing actual magnetic domain patterns. Samples of electron mirror micrographs of domain patterns of these materials are shown and compared with domain patterns of the same specimen areas obtained by the conventional powder technique. The identical nature of the configurations on both micrographs provided final proof of the feasibility of electron mirror microscopy in depicting magnetic patterns. Criteria required to distinguish magnetic patterns from those of electrical or relief origin are derived from the experimental findings and are verified by elementary theoretical considerations about magnetic contrast formation in electron mirror microscopy.