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When iron is evaporated in a dilute atmosphere of helium the deposit consists of very small particles whose size depends primarily on the helium pressure. If these particles are allowed to fall on to a ferromagnetic specimen they deposit preferentially at the domain boundaries. The Bitter patterns so formed can be examined optically or, for high resolution work, may be replicated and examined in the electron microscope.
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Hutchinson et al. (1965) studied this question.
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