Behavior of the irreversibility line in the new superconductor La<sub>1.5+xsub>Ba<sub>1.5+x鈭?span style='font-style: italic'>ysub>Ca<sub>ysub>Cu<sub>3sub>O<sub>zsub>
- 作者：C.A. Parra Vargas<sup>bsup> ; J.L. Pimentel Jr.<sup>csup> ; P. Pureur<sup>csup> ; D.A. Landí ; nez Té ; llez<sup>asup> ; J. Roa-Rojas<sup>asup><sup> ; sup><sup>carlos.parra@uptc.edu.cosup>
- 关键词：Magnetization ; Fluctuations
- 刊名：Physica B
- 出版年：2012
- 期刊代码：53_09214526
- 类别：ph
- 出版时间：15 August, 2012
- 卷：407
- 期：16
- 页码：3128-3130
- 文件大小：366 K
摘要
The irreversibility properties of high-T<sub>csub> superconductors are of major importance for technological applications. For example, a high irreversibility magnetic field is a more desirable quality for a superconductor . The irreversibility line in the H-T plane is constituted by experimental points, which divides the irreversible and reversible behavior of the magnetization. The irreversibility lines for series of La<sub>1.5+xsub>Ba<sub>1.5+x鈭?em>ysub>Ca<sub>ysub>Cu<sub>3sub>O<sub>zsub> polycrystalline samples with different doping were investigated. The samples were synthesized using the usual solid estate reaction method. Rietveld-type refinement of x-ray diffraction patterns permitted to determine the crystallization of material in a tetragonal structure. Curves of magnetization ZFC-FC for the system La<sub>1.5+xsub>Ba<sub>1.5+x鈭?em>ysub>Ca<sub>ysub>Cu<sub>3sub>O<sub>zsub>, were measured in magnetic fields of the 10-20,000 Oe, and allowed to obtain the values for the irreversibility and critical temperatures. The data of irreversibility temperature allowed demarcating the irreversibility line, T<sub>irrsub>(H). Two main lines are used for the interpretation of the irreversibility line: one of those which suppose that the vortexes are activated thermally and the other proposes that associated to T<sub>irrsub> a phase transition occurs. The irreversibility line is described by a power law. The obtained results allow concluding that in the system La<sub>1.5+xsub>Ba<sub>1.5+x鈭?em>ysub>Ca<sub>ysub>Cu<sub>3sub>O<sub>zsub> a characteristic bend of the Almeida-Thouless (AT) tendency is dominant for low fields and a bend Gabay-Toulouse (GT) behavior for high magnetic fields. This feature of the irreversibility line has been reported as a characteristic of granular superconductors and it corroborates the topological effects of vortexes mentioned by several authors .