We report on the analyses of fluctuation induced excess conductivity in the - behavior in the in situ prepared MgB2 tapes. The scaling functions for critical fluctuations are employed to investigate the excess conductivity of these tapes around transition. Two scaling models for excess conductivity in the absence of magnetic field, namely, first, Aslamazov and Larkin model, second, Lawrence and Doniach model, have been employed for the study. Fitting the experimental - data with these models indicates the three-dimensional nature of conduction of the carriers as opposed to the 2D character exhibited by the HTSCs. The estimated amplitude of coherence length from the fitted model is ~21？？. 1. Introduction Since the discovery of superconductivity in MgB2 there has been enormous research owing to its speculated potential applications. Though there has been extensive research on both scientific and technical aspects, but yet little attention was paid to the fluctuation induced [1–5] enhanced conductivity in MgB2. Superconductor transition broadening, induced by these fluctuations in the superconducting order parameter, is observed in various kinds of superconductors [6, 7]. Such broadening is normally due to superconducting fluctuation derived from a low dimensionality, short coherence length, and high . High , short coherence length, and low carrier densities impart an excess conductivity due to thermal fluctuation in the superconducting order parameter. There have been numerous studies on excess conductivity and order parameter fluctuations in (Y-123) [8–17], Bi2Sr2CaCu2 (Bi-2122), Bi2Sr2Ca2Cu2Cu3 (Bi-2223) [18–22], Tl2Ba2CaCu2 (Tl-2212) [23, 24], HgBa2Ca2Cu3 (Hg-1223), and HgBa2CaCu2 (Hg-1212) [25] systems, but only few reports exist on the fluctuation studies [26–28] in MgB2, and those are performed in the presence of magnetic field. The superconducting transition in the absence of fluctuations is characterized by a mean non zero value of the order parameter below the transition temperature and zero above the transition temperature. There are fluctuations in the order parameter both above and below the transition temperature, that is, there is a probability of Cooper pair formation even above the transition temperature. These fluctuations contribute to the various physical properties like electrical conductivity, diamagnetism and specific heat both above and below [29]. The effect of thermodynamic fluctuations on most of these properties is in the small range around and the study of fluctuation conductivity may also provide information regarding the
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