Electron diffraction covering a wide angular range from Bragg diffraction to small-angle diffraction. (9th April 2018)

• Record Type: Journal Article
• Authors: Nakajima, Hiroshi; Kotani, Atsuhiro; Harada, Ken; Mori, Shigeo
• Is Part Of: Microscopy. Volume 67:Number 4(2018)
• Page Start: 207
• Page End: 213
• Publication Date: 2018-04-09
• Subjects: Bragg diffraction -- small-angle electron diffraction (SmAED) -- magnetic materials -- Lorentz microscopy -- dark-field image -- phase transition; Microscopy -- Periodicals; 502.825
• DOI: 10.1093/jmicro/dfy019
• Languages: English
• ISSNs: 2050-5698

Abstract

Abstract : We constructed an electron optical system for observing both the Bragg diffraction and magnetic deflection in the same area with the objective lens turned off. This optical system was applied to analyze the magnetic microstructures and to observe the magnetic field-induced phase transition in three distinct magnets. Abstract: We construct an electron optical system to investigate Bragg diffraction (the crystal lattice plane, 10 −2 to 10 −3 rad) with the objective lens turned off by adjusting the current in the intermediate lenses. A crossover was located on the selected-area aperture plane. Thus, the dark-field imaging can be performed by using a selected-area aperture to select Bragg diffraction spots. The camera length can be controlled in the range of 0.8–4 m without exciting the objective lens. Furthermore, we can observe the magnetic-field dependence of electron diffraction using the objective lens under weak excitation conditions. The diffraction mode for Bragg diffraction can be easily switched to a small-angle electron diffraction mode having a camera length of more than 100 m. We propose this experimental method to acquire electron diffraction patterns that depict an extensive angular range from 10 −2 to 10 −7 rad. This method is applied to analyze the magnetic microstructures in three distinct magnetic materials, i.e. a uniaxial magnetic structure of BaFe10.35 Sc1.6 Mg0.05 O19, a martensite of a Ni–Mn–Ga alloy, and a helical magnetic structure of Ba0.5 Sr1.5 Zn2 Fe12 O22 .