Conductivity fluctuation in the high temperature superconductor with planar weight disparity Y_0.5Sm_0.5Ba₂Cu₃O_7−δ

Abstract

The synthesis of the Y 0.5 Sm 0.5 Ba 2 Cu 3 O 7−δ superconducting material by the standard solid state reaction is reported. DC resistivity measurements reveal the improvement of the critical temperature (T c ) when substitution of exact 50-50 mix of Yttrium and Samarium is performed. A bulk T c = 101 K was determined by the criterion of the maximum in the temperature derivative of electrical resistivity. Structure characterization by means the x-ray diffraction technique shows the crystalline appropriated distribution of Yttrium and Samarium to create substantial planar weight disparity (PWD) in alternating layers. This PWD increases T c in copper-oxide superconductors. In order to examine the effect of PWD on the pairing mechanism close to T c , conductivity fluctuation analysis was performed by the method of logarithmic temperature derivative of the conductivity excess. We found the occurrence of Gaussian and genuinely critical fluctuations. Our results are in agreement with reports on YBa 2 Cu 3 O 7-δ , but an enhancement of the Gaussian fluctuation regimes was experimentally detected as a result of the PWD. The correlations of the critical exponents with the dimensionality of the fluctuation system for each Gaussian regime were performed by using the Aslamazov-Larkin theory. The genuinely critical exponent is interpreted by the 3D-XY model as corresponding with the dynamical universality class of the E-model.

Effect of Ba-site substitution by Sr on ultrasonic velocity and electron–phonon coupling constant of DyBa2−xSrxCu3O7−δ superconductors

“…Instead, the reduction in the slope change of the step-like anomalies can be attributed to reduction in the degree of oxygen ordering. In addition, quite recently, elemental substitution in RE123 was reported to introduce some disparity in weight of insulating planes which in turn was suggested to cause the nonlinear drop in T c zero [27]. Additionally, our results, which showed a non-linear drop of T c with Sr substitution is also accompanied by a non-linear reduction of the slope change of the step-like anomalies.…”

“…In the case of RE123, Sr substitutions at the Ba site were reported to cause a non-linear drop in critical temperature, T c [25,26]. The slow decrease in T c was suggested to be related to changes in copper-oxygen bond length [25] or changes in planar weight distribution due to substitution of lighter Sr 2+ in place of heavier Ba 2+ [27]. Ultrasonic velocity studies on REBaCu 3 O 7−␦ were also able to identify accompanying bulk changes as a result of elemental substitutions [17,28] but the number of such studies is limited.…”

Effect of the oxygen distribution and inhomogeneity on the superconducting properties of YBa2Cu3O7−δ+xmol% Y2Ba4CuMoOysuperconductors

“…For further investigation of these effects the temperature derivative of resistivity is plotted in figure 7. The temperature value of the peak is close to the bulk critical temperature value T c , called the T c mean field (T cmf ) or pairing transition [29]. In this plot it is seen clearly that T c is not severely damaged by the addition of non-superconducting inclusion Y-24Mo1.…”