Anisotropic nature and scaling of thermally activated dissipation mechanism in Bi-2223 superconducting thin film
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This study deals with the resistive transition of the c-axis oriented Bi-2223 thin film produced on the single crystal MgO (100) substrate using direct current (DC) magnetron reactive sputtering technique at 100 watt in the case of applied field parallel and perpendicular to c-axis up to 3 T, respectively. Peak temperature (T-p) of the sample studied is determined from the variation of dR/dT as a function of temperature plot when the resistance called as R-p at the T-p is deduced from the same curve. It is found that the superconducting translation (onset and offset critical) temperatures reduce with the increment of the applied magnetic field strength and direction. In fact the minimum onset (T-c(onset)) value of 100.94 K and offset (T-c(offset)) value of 55.81 K are observed for 3 T applied field parallel to the c-axis. Moreover, the variation of Delta T-c(T-c(onset) - T-c(offset)) value is found to increase with the enhancement of the field and direction. Similar to the critical transition temperature results, the maximum variation (45.14 K) is observed for the sample in the applied field parallel to c-axis at 3 T. Further, the results obtained show that the dissipative resistivity is well adapted to thermally activated flux motion below the T-p value under the magnetic field and so the R-p values observed are used to examine the temperature and field dependence (mu H-0) of the flux pinning (activation) energy described as the formula U(T, mu H-0) = U-0(1 - T/T-p)H))H-m(-alpha). According to results, while m value is calculated to be about 1.572 and 1.492, alpha value is found to be about 0.546 and 0.498 at H//ab and H//c-axis, respectively, confirming that not only does the film produced show 3D-like behavior but also the thermally activated flux flow is the dominant mechanism on the sample. Additionally, the irreversibility fields (H-irr), upper critical fields (H-c2), penetration depths (lambda) and coherence lengths (xi) are evaluated from the magnetoresistance curves. When the anisotropy ratio of gamma(h) = xi(c)/xi(ab) is estimated to be about 6.42 at 0 K and 7.11 near the transition temperature (R = 0 Omega), the ratio of gamma(lambda) = lambda(c)/lambda(ab) is found to change from 1.97 until 3.28 in the range from 0 K to T-c. Based on the results obtained, it is concluded that both the anisotropy ratios are strongly dependent upon the temperature (particularly the ratio of lambda(lambda)) and the anisotropy ratio lambda(lambda) is more slightly smaller than that of gamma(h). (C) 2012 Elsevier B. V. All rights reserved.