Sandu V, Ionescu A M, Aldica G, Grigoroscuta M A, Burdusel M, Badica P
National Institute of Materials Physics, Street Atomistilor 405A, 077125, Magurele, Romania.
Sci Rep. 2021 Mar 15;11(1):5951. doi: 10.1038/s41598-021-85209-2.
An analysis of the field dependence of the pinning force in different, high density sintered samples of MgB is presented. The samples were chosen to be representative for pure MgB, MgB with additives, and partially oriented massive samples. In some cases, the curves of pinning force versus magnetic field of the selected samples present peculiar profiles and application of the typical scaling procedures fails. Based on the percolation model, we show that most features of the field dependence of the critical force that generate dissipation comply with the Dew-Hughes scaling law predictions within the grain boundary pinning mechanism if a connecting factor related to the superconducting connection of the grains is used. The field dependence of the connecting function, which is dependent on the superconducting anisotropy, is the main factor that controls the boundary between dissipative and non-dissipative current transport in high magnetic field. Experimental data indicate that the connecting function is also dependent on the particular properties (e.g., the presence of slightly non-stoichiometric phases, defects, homogeneity, and others) of each sample and it has the form of a single or double peaked function in all investigated samples.
本文对不同高密度烧结的MgB₂样品中钉扎力的场依赖性进行了分析。所选用的样品分别代表纯MgB₂、添加了添加剂的MgB₂以及部分取向的块状样品。在某些情况下，所选样品的钉扎力与磁场曲线呈现出特殊的轮廓，典型的标度程序在此失效。基于逾渗模型，我们表明，如果使用与晶粒超导连接相关的连接因子，在晶界钉扎机制内，产生耗散的临界力的场依赖性的大多数特征符合德休斯标度律预测。连接函数的场依赖性取决于超导各向异性，它是控制高磁场中耗散电流与非耗散电流传输边界的主要因素。实验数据表明，连接函数还取决于每个样品的特定性质（例如，存在轻微非化学计量比相、缺陷、均匀性等），并且在所有研究的样品中它具有单峰或双峰函数的形式。
