Hollow-Cone Foucault Imaging Method for Magnetic Structure Observations

Abstract

In conventional transmission electron microscopy (TEM), observation of magnetization structures and dielectric polarization structures are difficult to observe because these structures weakly interact with electron beams. Lorentz microscopy was developed to observe these structures effectively and practically. In Lorentz microscopy, however, Fresnel and Foucault imaging methods have the following disadvantages: in the Fresnel imaging method no additional contrast can be generated on the domains because of just defocusing for images and in the Foucault imaging method only the filtered out information can be obtained from selected domains. To overcome these difficulties, hollow-cone Foucault (HCF) imaging method was developed [1], where an incident electron beam on the specimen was tilted with respect to the optical axis and was circulated in all azimuths around the optical axis. Both magnetic domains and domain walls were simultaneously visualized with sufficient contrasts under the infocus condition. Furthermore, it was confirmed that schlieren imaging method [2], known as a highspeed imaging method applicable to low refractive index media, was realized.