Relationship between pinning mechanism and excess conductivity analysis of x wt% C4H6O5 (x=0.0, 4.0, and 6.0)-added bulk MgB2
Relationship between pinning mechanism and excess conductivity analysis of x wt% C4H6O5 (x=0.0, 4.0, and 6.0)-added bulk MgB2
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DOI：
10.1007/s10854-021-06538-6
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发表时间：
2021-07-07
影响因子：
2.8
通讯作者：
Savaskan, Burcu
中科院分区：
文献类型：
--
作者：
Cakir, Bakiye;Koparan, Ezgi Taylan;Savaskan, Burcu
采用两步固相反应法研究了添加x wt% C4H6O5（苹果酸）（x = 0.0、4.0和6.0）对块体MgB2超导体超导电性的影响。在0 T磁场下，电阻率测量从室温开始作为温度的函数进行。电阻率测量结果显示，随着添加比的增加，T-c没有显著变化。估计α是一个与本征电子相互作用有关的系数，发现添加样品的值大致相同，但发现纯样品的值较低；表明与加法的电子相互作用增加。为了分析MgB2的超导电性，采用Aslamazov和Larkin （AL）模型，研究了C4H6O5添加量对MgB2超导电性的影响。样品表明，在T-c以上和附近存在三种不同的波动机制。添加x wt%苹果酸（x = 4.0和6.0）的样品表现出HTSs的二维特性，而纯MgB2样品则表现出三维特性。虽然在纯样品中没有观察到T-LD，但在添加苹果酸的样品中可以观察到T-LD。随着添加量的增加，温度升高导致钉钉能力增强。对MgB2超导体的磁钉机理进行了详细的分析和讨论。在MgB2超导体中发现了常用的点钉和表面钉两种焊剂钉钉机制。此外，在低磁场区，所有样品都表现为正常的点钉钉，而在高磁场区，随着添加速率的增加，钉钉机制向表面钉钉转变。在加入苹果酸后出现团聚的样品中，观察到明显的二维波动，而在纯样品中观察到一维波动。由于团聚导致有效钉钉中心的存在，添加苹果酸的样品中二维波动占主导地位。
The influence of x wt% C4H6O5 (malic acid) (x = 0.0, 4.0, and 6.0) addition on excess conductivity in bulk MgB2 superconductors were fabricated by two-step solid-state reaction method. Resistivity measurements were carried out as a function of temperature starting from the room temperature at 0 T magnetic field. The electrical resistivity measurements did not show any significant change on T-c with the increasing addition ratio. Estimated alpha is a coefficient related with the intrinsic electronic interaction was found approximately the same value for added sample but pure sample was found to be lower; indicating increasing electronic interactions with addition. For the analysis of the excess conductivity, Aslamazov and Larkin (AL) model was used and the impacts of C4H6O5 additions on the excess conductivity of MgB2 have been investigated. The samples indicated the existence of three distinct fluctuation regimes above and near to T-c. The samples with x wt% malic acid additions (x = 4.0 and 6.0) showed 2D character such as exhibited by the HTSs, while the pure MgB2 sample exhibited the 3D nature. While the T-LD was not observed for pure sample, it was observed for malic acid-added samples. Also, the temperature value increased leading to growing pinning capability with the increasing addition ratio. Flux pinning mechanisms in MgB2 superconductor were analyzed and discussed in detail. Normal point pinning and surface pinning of flux pinning mechanisms were found to be effective in MgB2 superconductors. In addition, while all samples exhibited normal point pinning in the low magnetic field region, it was observed that the pinning mechanism shifted to the surface pinning with the increasing addition rate in the high magnetic field region. In the malic acid-added samples in which the agglomeration occurred, a dominant 2D fluctuation was observed while the 1D fluctuation was observed in the pure sample. Because the agglomeration causes existing of effective pinning centers, 2D fluctuations dominate in the malic acid-added samples.