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|Type:||Artigo de periódico|
|Title:||Disorder induced asymmetric magnetization in Bi2Sr2Ca2Cu3O10|
|Abstract:||Magnetization measurements as a function of external magnetic field H-c, temperature T and time t were performed in a c-axis-oriented bulk Bi2Sr2Ca2Cu3O10 compound sample with H-e applied along the preferential c-axis orientation. It is found that hysteresis loops, M(H-e), are asymmetric with respect to the equilibrium magnetization M-eq, such that an additional magnetization Delta M-m=M-m-M-eq arises for the flux entrance, where M-m(H-e)=1/2[M+(H-e)+M-(H-e)] is the cs mean magnetization, and M+, M-, the magnetization corresponding to the ascending and descending branches of the hysteresis loop, respectively. The time relaxation measurements made in H-e=1 T indicate that both M+(t) and M-(t) dependencies could be best described by the power law (M-M-infinity)similar to t(-beta), where M-infinity is obtained from the extrapolation of the relaxation law to tau=infinity. Above a 'depinning' temperature T-d approximate to 20 K, Delta M-m tends to zero, i.e. M-infinity(+)=M-eq, whereas at T <T-d, Delta M-m tends to the finite value M-g/2, and M-infinity(+)=M-eq+M-g. At the same time, M(infinity)(-)approximate to M-eq for all temperatures. Furthermore, it is shown that both Delta M, and M-g correlate well with the bulk vortex pinning, and that the found asymmetry can hardly be understood within frameworks of the classical Bean-Livingston surface barrier model. A possible physical picture for the disorder (pinning) induced asymmetry of both the hysteresis loops and the time relaxation is presented.|
|Editor:||Elsevier Science Bv|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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