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NANOSCALE FLUX PINNING SITES IN HIGH-Tc SUPERCONDUCTORS

Michael R. Koblischka 1Marc Winter 1A. Hu 2Miryala Muralidhar 2Uwe Hartmann 1M. Murakami 2,3

1. University of Saarbruecken, Institute of Experimental Physics (USAAR), P.O.Box 151150, Saarbr├╝cken 66041, Germany
2. International Superconductivity Technology Centre, Superconductivity Research Laboratory (SRL/ISTEC), 1-10-13, Shinonome, Koto-ku, Tokyo 135-0062, Japan
3. Department of Materials Science and Engineering, Shibaura Institute of Technology, 3-9-14, Shibaura,Minato-ku, Tokyo 108-8548, Japan

Abstract

Ideal flux pining centres in high-Tc superconductors should be of nanometre size as the coherence length, ξ, is so small. Therefore, the optimisation of high-Tc superconductor samples concerning high critical current densities and high flux pinning has to take place in the nanometre range. An important goal of the current research is to find specific preparation strategies to create such ideal flux pining sites already during the sample processing. By means of AFM and STM measurements at ambient conditions, we have investigated the topographies of various samples of YBa2Cu3Ox (YBCO), NdBa2Cu3Ox (NdBCO), (Sm,Eu,Gd)Ba2Cu3Ox (SEG) and (Nd,Eu,Gd)Ba2Cu3Ox (NEG) high-Tc superconductors. We find that the two systems with the highest critical current densities (NEG, SEG) and hence, the strongest flux pinning [1,2], exhibit microstructures on the nanometre scale which are remarkably different from those obtained in the YBCO system. The stripe-like growth structures observed in our topography measurements may be the key for the considerable improvements concerning the critical current densities especially at high magnetic fields and elevated operating temperature (77 K).

[1] A. Hu, N. Sakai, H. Zhou, M. Matsui, and M. Murakami, Supercond. Sci. Technol. 16 (2003) 33
[2] M. Muralidhar et al., Phys. Rev. Lett. 89 (2002) 237001

 

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Related papers

Presentation: poster at E-MRS Fall Meeting 2004, Symposium E, by Michael R. Koblischka
See On-line Journal of E-MRS Fall Meeting 2004

Submitted: 2004-04-30 15:28
Revised:   2009-06-08 12:55