Arab J Sci Eng DOI 10.1007/s13369-016-2164-9 RESEARCH ARTICLE - PHYSICS Fluctuation-Induced Conductivity of Carbon in Glucose-Doped MgB 2 Superconductor Intikhab A. Ansari 1 · Jafar M. Parakkandy 2 · M. Shahabuddin Shah 2 · Mohammed Shahabuddin 2 · Nasser S. Alzayed 2 Received: 17 November 2015 / Accepted: 14 April 2016 © King Fahd University of Petroleum & Minerals 2016 Abstract Fluctuation-induced conductivity (FIC) of glu- cose as a carbon-doped MgB 2 sample was investigated in the presence of a magnetic field in the range of 0–14T. Different concentrations (0–8 %) of glucose-doped MgB 2 samples were prepared using planetary dry ball milling and then employed standard solid-state reaction method on these samples. The prepared samples were characterized by X-ray diffractometer. The resistive transition broadening of all the samples becomes wider as the magnetic field was increased. The results of doped MgB 2 explained in terms of temperature derivative of the resistivity, dρ/dT with temperature. The mean field transition temperature (T mf c ) has been taken from the peak of the temperature derivative of resistivity plot for different doped samples. It is clear that T mf c of dρ/dT shifted to lower temperature region as we increase the magnetic field of the doped samples. Lawrence and Doniach model has been employed for the present study. The variation of FIC against inverse reduced temperature (ε −1 ) for different concentra- tions of glucose-doped MgB 2 samples was measured with varying applied field. The enhancement of coherence length observed as we decrease the value of T c and T mf c for 5 and 8 % C in glucose-doped MgB 2 samples when subjected to a different field. Keywords Fluctuation-induced conductivity · Magnesium diboride · Carbon doping · Transition temperature · Resistivity B Intikhab A. Ansari intikhabansari@yahoo.com 1 Department of General Studies, Jubail Industrial College, P. O. Box - 10099, Jubail 31961, Saudi Arabia 2 Department of Physics and Astronomy, College of Science, King Saud University, P. O. Box - 2455, Riyadh 11451, Saudi Arabia 1 Introduction Since the discovery of superconductivity in MgB 2 at 39 K, numerous studies have been revealed for its fundamental as- pects as well as its potential applications in several fields [1–4]. The MgB 2 have exclusive two-band nature that plays the remarkable role in superconducting state [5–7] in ad- dition to normal state [8–10]. As we know, MgB 2 have a simple crystal structure and the previous report described that the B–B planes are similar to CuO 2 planes in high T c cuprates [11]. Fabris et al. [12] described the temperature derivative of resistivity of MgB 2 sample in the vicinity of the critical temperature, T c . Sidorenko et al. [13] have in- vestigated the resistive transition broadening of thin films of MgB 2 using by thermally activated flux flow mechanism. The pristine bulk MgB 2 possesses low J c at high magnetic fields due to weak pinning centres and low upper critical field [2]. Therefore, various attempts had been adopted for the enhancement of H c2 and relatively high J c in the dirty thin film of MgB 2 [14, 15]. These include irradiation [16, 17], thermo-mechanical processing [18–21], and chemical dop- ing [22–33]. Particularly, the later technique seems to be effective to ameliorate the performance of MgB 2 supercon- ductor. Enormous organic [34–44] and inorganic sources [45–52] of reactive carbon (C) have been endeavoured to elevate the significant J c - H behaviour. Moreover, the dop- ing of nano-metal oxide has been reported to improve the noteworthy performance of MgB 2 superconductor [22, 25]. In the present study, we have investigated the fluctuation- induced conductivity (FIC), σ , for carbon in glucose-doped MgB 2 superconductor with different concentrations of C from 0–8 % in the presence of magnetic field from 0 to 14 T. Glucose is a carbohydrate and possesses a molecular formula C 6 H 12 O 6 , whose five hydroxyls (OH) groups are assembled in an unusual way along its six-C backbone. The temperature 123