A method to separate bulk and surface hysteresis contributions in HTSC powder by particle size classification and its application to Hg(Re)-1223

• Published in: Physica. C, Superconductivity Superconductivity, 1999-02, Vol.313 (1), p.21-28
• Main Authors: Krelaus, J., Hoffmann, J., Heinemann, K., Freyhardt, H.C.
• Format: Article
• Language: English
• Subjects: Bulk hysteresis; HTSC powder; Particle size classification; Surface hysteresis
• ISSN: 0921-4534; 1873-2143
• DOI: 10.1016/S0921-4534(98)00680-7

A particle size classification method is developed to separate bulk pinning from pinning at surface barriers in high- T c superconducting (HTSC) powder material. The powder is fractionized into particle-size classes by passing it through sieving cascades. An analysis of magnetic hysteresis loops in the different particle size classes is performed on the basis of a Bean-like critical state model including surface-barrier induced irreversibility of the magnetization. This leads to a quantitative separation of the respective contributions to total hysteresis. The method is tested with Y-123 and applied to Hg(15%Re)-1223. The surface contribution to irreversibility in the Hg-based HTSC significantly exceeds that of Y-123. It approximately follows the reciprocal field dependence, μ 0Δ M= B p 2/ B 0, of the Clem model. Surface barriers provide the major contribution to irreversibility in Hg-based HTSC powder. The method brings a new, self-consistent evidence for strong surface barriers being a characteristic property of Hg-based HTSC.