High-voltage Lorentz electron microscopy of Fe-Nd-B magnets (abstract)

Abstract

Magnetic domains in recently developed Fe-Nd-B permanent magnets have been investigated by high-voltage Lorentz electron microscopy to understand the interaction of domain walls with microstructural features. Specifically, the interaction of the domain walls with the nonmagnetic fcc phase and grain boundaries have been investigated. Samples with the c axis in the plane of the foil and normal to it have been investigated. Domain wall widths have been measured from defocussing experiments in the Fresnel mode. The wall widths experimentally determined compare well with those predicted from theoretical calculations. In the case of foils with the c axis in the plane of the foil, the domains are wider. Also, the domain wall image width changes from point to point, although there is no change in foil thickness. The walls in these foils could be moved by tilting the foil (thus varying the in-plane field of the objective lens). By this method, the interaction of the domain walls with microstructural features was studied. Results of all these experiments will be presented in this paper.