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The development of coherent Foucault imaging to investigate magnetic microstructure
Author(s) -
JOHNSTON A. B.,
CHAPMAN J. N.
Publication year - 1995
Publication title -
journal of microscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.569
H-Index - 111
eISSN - 1365-2818
pISSN - 0022-2720
DOI - 10.1111/j.1365-2818.1995.tb03621.x
Subject(s) - microstructure , development (topology) , materials science , nuclear magnetic resonance , physics , metallurgy , mathematics , mathematical analysis
SUMMARY We describe coherent Foucault (CF) imaging, a novel TEM technique which we have used successfully to investigate quantitatively micromagnetic structures in thin magnetic films. A simple analytical approach to CF imaging shows how an accurately positioned aperture in the diffraction plane leads to a magnetic interferogram forming in the image plane. Fringes follow lines of magnetic induction and there is one quantum of flux, h/e , between adjacent fringes. The aperture used can either be opaque or phase‐shifting and one‐ and two‐dimensional computer simulations have been performed to investigate how the nature and positioning of the aperture, along with the coherence of the illumination, affect the detailed form of the interferogram. Images recorded on a modified Philips CM20 FEG TEM confirm the simulations and demonstrate the power of the technique. The paper ends with a brief discussion of the broader uses of Foucault imaging.