Magnetization and relaxation in Hg-1223: bulk vs. surface irreversibility, anisotropy and the influence of Re-doping

• Published in: Physica. C, Superconductivity Superconductivity, 1999-03, Vol.314 (1), p.81-92
• Main Authors: Krelaus, J., Reder, M., Hoffmann, J., Freyhardt, H.C.
• Format: Article
• Language: English
• Subjects: Anisotropy; Hg-1223; Re-doping; Relaxation; Surface barrier
• ISSN: 0921-4534; 1873-2143
• DOI: 10.1016/S0921-4534(99)00149-5

Particle-size fractionization is used to separate bulk and surface hysteresis in pure and Re-doped Hg(15%)-1223. Re-doped samples have smaller surface barriers and higher bulk current densities than undoped Hg-1223. Neutron-irradiated samples exhibit practically no surface barrier effect. A `pinning roughness' model is suggested to unify the observations. The fractionization technique is extended to relaxation of magnetically aligned Hg-1223. In wide temperature regions, both surface and bulk currents do relax. However, near the irreversibility temperature, bulk currents decay to zero, whereas surface relaxation continues. Relaxation is a complex interplay of bulk/surface effects, which subsequent investigations in this field must regard. From magnetization measurements on magnetically oriented samples, anisotropy parameters are estimated to γ≈9±3 (Hg-1223) resp. γ≈4.5±2 (Hg(15% Re)-1223). This is a very drastic effect of Re-doping on the superconducting properties of Hg-1223.