An H–T diagram characterizing the activation barriers obtained from the magnetic relaxation of HgBa2Ca2Cu3O8+ thin film
Abstract:The magnetic relaxation of an epitaxial HgBa2Ca2Cu3O8+ (Hg-1223) thin film was measured at several fields and temperatures. After the activation energy and the normalized relaxation rate had been analysed, the U–j characteristics were mapped on the H–T diagram. The power-law region with a creep exponent of &\mu \simeq 7/9 ;, which indicates large bundle creep, became a logarithmic region in the small limit as j went far below jc. From this analysis, we found that a large bundle of flux acts like a single vortex, the size of which was temperature independent. This behaviour is quite different from that of other cuprate superconductors. Also, the crossover temperature, Tb, between the power-law and the logarithmic regions was inversely proportional to H. The fitting of Tb() on the H–T diagram is in good agreement with the field exponent of &\beta \simeq 0.4 ; that was obtained from the scaling of Ueff(H).
Document Type: Research Article
Publication date: June 1, 2005