Resumen

ROA-ROJAS, J.; ORLANDO, M.T.D.; BAGGIO-SAITOVICH, E.  y  PUREUR, P.. Magnetotransport properties of Hg_1-xRe_xBa₂Ca₂Cu₃O_8+δ superconductors. Rev. mex. fis. [online]. 2002, vol.48, n.2, pp.118-122. ISSN 0035-001X.

Systematic measurements on Hall and longitudinal resistivities as a function of temperature in Hg_1-xRe_xBa₂Ca₂Cu₃O_8+δ (x=0.18) ceramic samples were effectuated. These measurements were performed in magnetic fields H=0, 10, 20, 40 and 50 kOe, applied perpendicularly to the transport current orientation. In the normal phase, the Hall coefficient is positive and may be accurately fitted to R_H = 1/aT + b. The Hall angle varies approximately as predicted by Anderson's formula. When the temperature approaches from above the mean-field critical temperature T_c, the Hall resistivity decreases abruptly as a consequence of thermal fluctuations. Below T_c and for H = 10and 20 kOe, the Hall response changes signal, going passing through a minimum and becoming positive again before the zero resistance state is obtained. For stronger applied fields, the Hall resistivity remains positive in the mixed phase, though its qualitative shape, preserving the local minimum below T_c. We ascribe the double sign reversal feature to combined effects of thermal fluctuations and vortex motion. Close to the zero resistance state, the Hall resistivity varies as a power law of the longitudinal resistivity, with a field-independent exponent. This result may be interpreted as evidence of a vortex-glass transition.

Palabras llave : Superconductivity; Transport Properties; Mixed State.

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