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

Particle-size fractionization is used to separate bulk and surface hysteres is in pure and Re-doped Hg(15%)-1223. Re-doped samples have smaller surface barriers and higher bull; current densities than undoped Hg-1223. Neutron- irradiated samples exhibit practically no surface barrier effect. A 'pinnin g roughness' model is suggested to unify the observations. The fractionizat ion 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, wherea s surface relaxation continues. Relaxation is a complex interplay of bulk/s urface effects, which subsequent investigations in this field must regard. From magnetization measurements on magnetically oriented samples, anisotrop y parameters are estimated to gamma approximate to 9 +/- 3 (Hg-1223) resp. gamma approximate to 4.5 +/- 2 (Hg(15% Re)-1223). This is a very drastic ef fect of Re-doping on the superconducting properties of Hg-1223. (C) 1999 Pu blished by Elsevier Science B.V. All rights reserved.