Evaluation of magnetotransport properties of Au added YBCO ceramics: combination of experimental and advanced theoretical approaches

The purpose of this work is to investigate the change of flux pinning ability, superconducting and physical properties of gold particle addition in the YBa 2 Cu 3 O 7-x (YBCO) superconducting matrix using temperature dependent resistivity measurements under different applied magnetic fields; namely 0.0, 0.3, 1.0, 2.0, 5.0 and 7.0 T. The room temperature resistivity, transition temperature ( T c ), transition width ( ∆T c ) and mobile hole carrier concentration values for each sample have separately been determined. In addition, we estimated the field-dependent activation energy ( U 0 ), irreversibility field ( µ 0 H irr ), upper critical field ( µ 0 H c2 ), penetration depth ( λ ) and coherence length ( ξ ) with the quantum mechanical approaches related to the fluxoid mechanism for all the samples prepared. It was found that the flux pinning energy values evaluated by Thermally Activated Flux Creep (TAFC) model were determined to be about 11,455 K, 13,413 K, 10,350 K and 9320 K for the undoped, 1 wt%, 5 wt% and 20 wt% Au doped samples, respectively. Moreover, the results obtained showed that the critical temperature, activation energy, irreversibility and upper critical field values were found to depend strongly on the gold content and applied magnetic field strength. The values of µ 0 H irr , µ 0 H c2 , λ and ξ ( ∆T c ) initially exhibited a slight increment (decrement) followed by a decrease (increase) for the samples with the higher gold-doping concentrations. The possible reasons regarding the observed changes in flux pinning and fundamental superconducting properties due to gold-doping in YBCO superconductors were discussed in detail. We indicated that a certain amount of gold doping has an effective role to form the nucleation centers that serve as the active flux pinning regions in the YBCO system so that the quality of interaction between the superconducting grains and inter-granular coupling strength in the adjacent multilayers can increase remarkably.