Foucault imaging and small-angle electron diffraction in controlled external magnetic fields

TL;DR

This paper presents a method for capturing Foucault images and small-angle electron diffraction patterns in external magnetic fields using a standard transmission electron microscope, enabling visualization of magnetic domains in ferromagnetic oxides.

Contribution

The authors developed a technique to control external magnetic fields in a conventional electron microscope for imaging magnetic domains without modifications.

Findings

Magnetic domains in La0.7Sr0.3MnO3 and Nd0.5Sr0.5MnO3 were visualized.

Pinning of magnetic domain walls at twin boundaries affects domain formation.

External magnetic fields influence magnetic domain structures in ferromagnetic oxides.

Abstract

We report a method for acquiring Foucault images and small-angle electron diffraction patterns in external magnetic fields using a conventional transmission electron microscope without any modification. In the electron optical system that we have constructed, external magnetic fields parallel to the optical axis can be controlled using the objective lens pole piece under weak excitation conditions in the Foucault mode and the diffraction mode. We observe two ferromagnetic perovskite-type manganese oxides, La$_{0.7}$Sr$_{0.3}$MnO$_{3}$ and Nd$_{0.5}$Sr$_{0.5}$MnO$_{3}$, in order to visualize magnetic domains and their magnetic responses to external magnetic fields. In rhombohedral-structured La$_{0.7}$Sr$_{0.3}$MnO$_{3}$, pinning of magnetic domain walls at crystallographic twin boundaries was found to have a strong influence on the generation of new magnetic domains in external applied magnetic fields.