Study of the Magnetic Leakage Field in Cobalt by means of a Divergent Electron Beam

Abstract

THE leakage field due to the magnetic domains in an unmagnetized single crystal of hexagonal cobalt has been shown to produce various effects on an electron beam¹. A new method for the study of this leakage field using a divergent electron beam has been developed recently. The electron beam of a conventional electron diffraction apparatus is limited as before by a small movable aperture of 6–25µ, close to the crystal. The crystal face is adjusted to an angle of glancing incidence between a fraction of a degree and a few degrees. Immediately below the aperture are fixed on to the same holder two parallel metal plates, to which an alternating potential difference is applied. A beam is thus provided which diverges from a point close to the aperture in a direction parallel to the crystal edge. This beam scans at the level of the specimen a region which is extended in a direction parallel to the crystal edge, but which is only of the width of the aperture in a direction normal to it. The electrons of this beam are deflected by the magnetic leakage field existing in this region.