Observation of Vortices and Columnar Defects by 1-MV Lorentz Microscopy I
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Observation of Vortices and Columnar Defects by 1-MV Lorentz Microscopy I H. Kasai1,5, O. Kamimura1,5, T. Matsuda1,5, K. Harada1,5, A. Tonomura1,5, S. Okayasu4, M. Sasase4, Y. Nakayama2,5, J. Shimoyama2,5, K. Kishio2,5, T. Hanaguri3,5 and K. Kitazawa3,5 1
Advanced Research Laboratory, Hitachi Ltd., Hatoyama, Saitama 350-0395, JAPAN Department of Applied Chemistry, University of Tokyo, Bunkyo, Tokyo 113-8656, JAPAN 3 Department of Advanced Materials Science, School of Frontier Science, University of Tokyo, Bunkyo, Tokyo 113-0033, JAPAN 4 Department of Material Science, Japan Atomic Energy Research Institute (JAERI), Tokai, Naka-gun, Ibaraki 319-1195, JAPAN 5 CREST, Japan Science and Technology Corporation (JST), Kawaguchi, Saitama 332-0012, JAPAN 2
ABSTRUCT A single crystalline Bi2Sr2CaCu2O8+δ which has columnar defects in its inside are observed by Lorentz microscopy using the newly developed 1-MV field emission electron microscope at the first time. The superconducting vortices are observed with higher contrast than ever. Simultaneous observation of vortices and columnar defect is succeeded in real time. INTRODUCTION An understanding of the dynamic behavior of individual vortices (magnetic flux lines) in a Type-II superconductor is important for developing practical applications of superconductivity, because the vortex flow generates heat and breaks down the superconducting state. Several methods of observing vortices had been tried and carried out, however the direct and dynamical observation of them is very difficult. For example, scanning tunneling microscopy has succeeded to just show the static condition [1] and Bitter decoration method has also showed it as replica [2]. Lorentz microscopy with a 300-kV field-emission electron microscope has succeeded to observe each single vortex and their dynamics by TV rate [3], and the pinning effect by columnar defects was observed semi-macroscopically in our previous work [4]. Here we report the first observation of vortices using newly developed 1-MV field emission electron microscope [5] whose world highest brightness is 2 x 1010 A/cm2sr.
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EXPERIMENTAL Figure 1 shows out view of the 1-MV field emission electron microscope which could record the world finest lattice fringes of 49.8 pm of gold crystal (Fig. 2) [5]. In case of observation of vortices in high-temperature superconductor Bi2Sr2CaCu2O8+δ (Bi-2212), the observable specimen thickness by 300-kV electron microscope is about 200 nm at maximum [6], while the 1-MeV electrons can be penetrate the 400-nm-thick specimen whose size is similar to the vortex diameter (twice the penetration depth of Bi-2212) [7]. Higher contrast and detail images of the vortices are able to observe by the new microscope.
Figure 2 The electron micrograph of 49.8 pm spacing fringes in an Au(111) thin film [7].
Figure 1 Out view of the 1-MV field emission electron microscope [8].
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A single crystalline of Bi2Sr2CaCu2O8+δ (Bi-2212) was grown by the standard floating-zone technique and annealed at 800 degrees in Celsius f
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