Development of observation methods for nano-sized magnetic domains with electron holography

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The target of the present works is to develop a new technique of in situ observations with electron holography and apply the new techniques to studies of magnetic domains in advanced materials. The results are summarized as follws:1.A new apparatus with a small hall probe was developed, which enables us to measure the magnetic field inside the objective lens. This apparatus has revealed the relation between the magnetic field near the specimen and the electric current of the objective lens so that magnetic domains can be observed in a wide range of the applied magnetic field.2.Experimental conditions to observe electron holograms were optimized by operating the electromagnets installed in the electron microscope. Visibility of the holograms was much improved.3.A technique to separate the magnetic information in holograms from the electric information (the effect of mean inner potential) was established. The electric information can be eliminated by numerical analyses of two digitized holograms, which are obtained in magnetic and nonmagnetic states, respectively.4.The new techniques were applied to studies of magnetization distribution in a perovskite-type manganite, which exhibits the well-known colossal magnetoresistance. Distribution of magnetic flux was directly observed in a magnetically phase-separated state. The results shed light on understanding of the conduction mechanism of hole-doped manganites.