FIZIKA A 8 (1999) 4 , 319-332

IRREVERSIBILITY LINE OF Bi2223/Ag TAPE IN HIGH MAGNETIC FIELDS

IVICA KUŠVIĆ^a, EMIL BABIĆ^a, JOHN R. COOPER^b, WEI GUO WANG^c,
HUA KUN LIU^c and SHI XUE DOU^c

^aDepartment of Physics, Faculty of Science, University of Zagreb, 10000 Zagreb, Croatia

^cCentre for Superconducting and Electronic Materials, University of Wollongong, Wollongong, NSW 2522, Australia

Dedicated to Professor Boran Leontić on the occasion of his 70^th birthday

Received 23 November 1999; Accepted 10 April 2000

The magnetoresistance of a (Bi,Pb)₂Sr₂Ca₂Cu₃O_10+y Ag sheathed tape was measured in the temperature range 15 K Ł T Ł 120 K and magnetic field B Ł 15 T applied perpendicular to the broader surface of tape. Throughout the explored field range, the onset of resistivity shows Arrhenius behaviour r µ exp(-U^*(1-T/T_cs)/k_BTB^0.5) where U^* is the sample dependent constant, and T_cs is the temperature somewhat higher than the temperature of the resistivity onset. The observed resistance variation can be attributed to a thermally activated flux flow in a highly viscous vortex-liquid regime characterized by a plastic deformation of vortices. Experimentally determined resistive irreversibility line B_irr vs. T_irr follows the power-law dependence B_irr(T_irr) µ (T_cs/T_irr-1)² which can be derived from the exponential behaviour of resistivity. Our B_irr(T_irr) data can also be fitted by the combination of the Josephson coupling model and depinning of pancake vortices. This fit provides very reasonable values for B_c2, B_c1, B_c, x_ab and l_ab of Bi2223 compound, and removes the unphysical divergence of B_irr(T® 0) resulting from the above power-law fit.

PACS numbers: 74.25.Fy, 74.60.Ge, 74.72.Hs
UDC 538.945

Keywords: (Bi,Pb)₂Sr₂Ca₂Cu₃O_10+yAg sheathed tape, magnetoresistance, viscous vortex-liquid regime, resistive irreversibility line

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