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Dynamic Observation of Vortex Interaction with Pinning Centers Using Electron Waves

Published online by Cambridge University Press:  02 July 2020

Akira Tonomura
Akira Tonomura*
Affiliation:
Advanced Research Laboratory, Hitachi, Ltd. Saitama, 350-03, Japan
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Tiny magnetic vortices hold the key in practical applications of superconductors, since the dynamic behaviors of vortices at pinning centers determine the critical current. These vortices have become observable directly and dynamically by using a “coherent” field-emission electron beam: The magnetic lines of force of vortices can be quantitatively observed as contour fringes in an electron-holographic interference micrograph. The change in the vortex radius could actually be measured when the temperature of a superconducting thin film changed. Vortices were also dynamically observed in a Lorentz micrograph. Both vortices and defects in the thin film can be observed simultaneously with this method, though the defects image is blurred.

This paper reports the dynamic observation of vortices at defects when the applied magnetic field changes. A superconducting Nb thin film, set on a low-temperature stage, is tilted 45° to an incident beam of 300kV electrons (see Fig. 1), and an external magnetic field is applied in the horizontal direction. When an electron beam passes through the vortices, their magnetic fields deflect the electron beam. Therefore, when observed in the lower plane, a vortex can be viewed as a pair of black and white spots.

Type
In Situ Studies in Microscopy
Information
Microscopy and Microanalysis , Volume 3 , Issue S2: Proceedings: Microscopy & Microanalysis '97, Microscopy Society of America 55th Annual Meeting, Microbeam Analysis Society 31st Annual Meeting, Histochemical Society 48th Annual Meeting, Cleveland, Ohio, August 10-14, 1997 , August 1997 , pp. 585 - 586
Copyright
Copyright © Microscopy Society of America 1997

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References

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