Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
1521294 | Materials Chemistry and Physics | 2015 | 9 Pages |
Abstract
We compare the electrical magneto-conductivity fluctuation between YBa2Cu3Oy (Y-123) and YBa2Cu3Oy embedded by an Y-deficient Y-123 nano-phase, generated by planetary ball-milling. Both samples were synthesized by solid state reaction with two stages of sintering at 950 °C and separated by energetic milling (milled sample) and hand grinding (unmilled sample). SEM analysis of the milled samples shows the appearance of spherical shaped nano-entities of Y-deficient Y-123 embedded in the Y-123 matrix. The magneto-conductivity data are analysed in terms of the temperature derivative of the resistivity and the logarithmic temperature derivative of the conductivity. The results show the occurrence of two-stage transitions: intragranular and intergranular, as well as a pairing transition splitting in the milled sample related to the presence of the Y-deficient nanoparticles. In the normal state, we identify a contribution of the Gaussian regimes for both samples. In the presence of a high magnetic field, the critical exponent near Tco of the milled material is higher than the one of the unmilled, indicating that the nanoparticles strengthen the effects of the order-parameter phase of individual grains of the Y-123 strongly disordered. This result fits well into a description based on a dirty limit of the general vortex-glass theory. In the paracoherent state, a crossover occurs and a small temperature range appears where the fluctuation conductivity may be governed by others mechanisms related to vortices dynamics. This temperature range is smaller in the milled sample.
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Physical Sciences and Engineering
Materials Science
Electronic, Optical and Magnetic Materials
Authors
E. Hannachi, Y. Slimani, M.K. Ben Salem, A. Hamrita, D.K. Mani, M. Ben Salem, F. Ben Azzouz,