Volume 4, Issue 2 (6-2004)                   IJPR 2004, 4(2): 125-172 | Back to browse issues page

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M. R. Mohammadizadeh and M Akhavan, M Akhavan. Structural, electronic and flux dynamics of Gd(Ba2-xPrx)Cu3O7+& delta superconductor. IJPR. 2004; 4 (2) :125-172
URL: http://ijpr.iut.ac.ir/article-1-369-en.html
Abstract:   (36210 Views)

  The Gd(Ba2-xPrx)Cu3O single phase polycrystalline samples with 0.00 ≤ x ≤ 1.00 were investigated for structural, electronic and flux dynamic properties. An unusual hump on the resistivity vs. temperature curve of the samples has been observed for particular values of Pr doping. We have found that the Ba atom substitution at the rare earth site could lead to superconductivity in some parts of the grains at Tm~80-90K, which appears as a hump on the (T) curve. For all the samples, the two-dimensional variable range hopping (VRH) is a dominant conduction mechanism in the normal state. The Pr doping strongly localizes the carriers in the normal state, and finally causes the suppression of superconductivity. The effect of Pr substitution in 123 structure of HTSC at R or Ba site is to increase the pseudo gap temperature Ts, although, Pr at Ba site has a stronger effect on the increase of Ts and suppression of superconductivity. We have also extracted the two dimensionality aspects of HTSC through the similarities between superconductors, two-dimensional electron gas (2D-EG) i.e., MOSFETs, and the ultra thin films of conventional superconductors. The magneto resistance of the samples have been studied within thermally activated flux creep and the Ambegaokar and Halperin phase slip models. The derived critical current density, Hc2(T), Hc2(0), and superconducting coherence length show that the Pr- doping, like weak links, decreases the vortex flux pinning energy. Our results imply that understanding the real suppression mechanism of superconductivity by Pr doping in HTSC is connected unavoidably to determination of the exact position of Pr in the structure.

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