Nanoengineering of flux pinning sites in high-Tc superconductors

Research output: Contribution to journalArticle

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Abstract

Volume pinning forces were determined for a variety of bulk high-7c superconductors of the 123-type from magnetization measurements. By means of scaling of the pinning forces, the acting pinning mechanisms in various temperature ranges were identified. The Nd based superconductors and some YBCO crystals exhibited a dominating pinning of the δ Tc-type (i.e., small, superconducting pinning sites). In contrast to this, the addition of insulating 211 particles provided pinning of the δl-type; providing effective pinning in the entire temperature range acting as a 'background' pinning mechanism for the peak effect. Due to the small coherence lengths of the high- Tc compounds, effective pinning sites are defects or particles of nanometer size relative to ξ3. Integral magnetic measurements of the magnetization as a function of temperature in large applied magnetic fields (up to 7 T) revealed that practically all high- Tc compounds were spatially inhomogeneous, which could be caused by oxygen deficiency (YBCO), solid solutions of Nd/Ba (NdBCO and other light rare earth compounds), intergrowths (Bi-based superconductors), and doping by pair-breaking dopants like Zn, Pr. This implies that the superconducting sample consists of stronger and weaker superconducting areas, coupled together. In large applied fields, this coupling gets broken and the magnetization versus temperature curves revealed more than one superconducting transition. In contrast, irradiation experiments by neutrons, protons, and heavy-ions enabled the artificial introduction of very effective pinning sites into the high- Tc superconductors, thus creating a large variety of different observations using magnetic data. From all these observations, we construct a pinning diagram for bulk high- Tc superconductors explaining many features observed in high- Tc samples.

Original languageEnglish
Pages (from-to)280-291
Number of pages12
JournalTsinghua Science and Technology
Volume8
Issue number3
Publication statusPublished - 2003 Jun 1
Externally publishedYes

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flux pinning
magnetization
rare earth compounds
temperature
hypoxia
magnetic measurement
heavy ions
solid solutions
diagrams
scaling
neutrons

Keywords

  • Critical current densities
  • Flux pinning
  • Nanoengineering of pinning sites
  • Peak effect
  • Spatial variations of the transition temperature

ASJC Scopus subject areas

  • General

Cite this

Nanoengineering of flux pinning sites in high-Tc superconductors. / Koblischka, Michael Rudolf.

In: Tsinghua Science and Technology, Vol. 8, No. 3, 01.06.2003, p. 280-291.

Research output: Contribution to journalArticle

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