Different regions of fluctuation conductivity in unirradiated and alpha-irradiated Bi2Sr2CaCu2O8+δ and (Bi,Pb)2Sr2CaCu2O8+δ superconductors

Udayan, De ; Mandal, K. ; Sanyal, D. ; Majumdar, C. K. (2000) Different regions of fluctuation conductivity in unirradiated and alpha-irradiated Bi2Sr2CaCu2O8+δ and (Bi,Pb)2Sr2CaCu2O8+δ superconductors Physica C: Superconductivity, 339 (2). 113-119 . ISSN 0921-4534

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Official URL: http://linkinghub.elsevier.com/retrieve/pii/S09214...

Related URL: http://dx.doi.org/10.1016/S0921-4534(00)00337-3

Abstract

Radiation damage in Bi-2212 and (Bi0.92Pb0.17)-2212 superconducting pellets due to irradiation by 40 MeV He++-beam has been studied, as these two compounds differ with respect to lattice strain in their Bi-O and (Bi,Pb)-O layers. These samples were prepared with excess oxygen that accounts for their lowered superconducting transition temperature, Tc, of 59.5 and 64.5 K, respectively. Irradiation to 8.14×1015 He++/cm2raised Tcby 4.5 and 5.5 K, respectively, and also their normal state resistivities. Excess conductivity analysis for the unirradiated and irradiated samples showed (i) a transition of the conductivity fluctuation from 2D (λ=1.0) to 3D (λ=0.5) behaviour, on cooling across a temperature T0, and (ii) also the signature (λ=3.0) of critical fluctuations in a network of superconducting microregions, for temperatures below Tcr, where Tcr is seen to be 5 to 10 K lower than T0. The rise in Tchas been explained from irradiation-induced removal of oxygen taking the hole concentration towards the value for the peak in Tc.

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