Electron Microscope Observations of Ferromagnetic Domains in Chromium Tribromide

Publisher Website
Google Scholar
Abstract
A liquid‐helium object stage for the electron microscope has been used to observe directly magnetic domains in CrBr3, an ionic ferromagnet with a Curie point of 36°K. Some of the contrast effects observed are typical of the magnetic‐domain wall observations made by Lorentz microscopy on materials such as Co which are similar magnetically to CrBr3. The more common contrast effects are contiguous black and white lines which correspond to the domains directly and look similar to observations with the optical Faraday effect. These effects occur with the objective lens far off focus. Evidence that the effects are due to magnetic domains includes disappearance of the structure in in‐focus micrographs and disappearance on warming the specimen through the Curie point. The scale of the domain structure is ∼200–2000 Å, consistent with specimen thicknesses ∼1000 Å and a foil orientation with the c axis normal to the plane of the foil. The observations corroborate the domain structure deduced by Dillon et al. from magneto‐optical studies for thicker specimens of this material.