Department of Physics 'E.R. Caianiello', University of Salerno, via Giovanni Paolo II, 132, Fisciano (SALERNO), I-84084, Italy. CNR-SPIN Salerno, via Giovanni Paolo II, 132, Fisciano (SALERNO), I-84084, Italy.
Nanotechnology. 2019 Jun 21;30(25):254001. doi: 10.1088/1361-6528/ab0c23. Epub 2019 Mar 4.
The measurements of DC magnetization M as a function of magnetic field (H) and time (t) have been performed in order to study the superconducting and pinning properties of a Fe(Se, Te) iron based superconductor fabricated by means of the Bridgman technique. By performing the superconducting hysteresis loops M(H) at different temperatures in the case of perpendicular and parallel field, the critical current density J (H) has been extracted in the framework of the Bean critical state model for both configurations. The J (H) curves have shown the presence of the second magnetization peak effect that causes an anomalous increase in the field dependence of the critical current density. In order to obtain the J anisotropy of the sample, we have performed the ratio between perpendicular and parallel critical current density values [Formula: see text] and compared its values with the literature ones. The information regarding the pinning energy U have been extracted by means of the relaxation of the irreversible magnetization M(t) in the case H∣∣c. In particular, performing relaxation measurements at different temperatures and magnetic fields, the temperature dependence of the pinning energy U(T) at different magnetic fields has been obtained showing an anomalous temperature scaling of the curves. The presence of a maximum in the U(T) curves suggests a pinning crossover at a given field and temperature H (T). The H (T) values have been fitted with the equation H (T) = H (0) (1 - T/T*) whose results confirm the correlation between the elastic/plastic crossover and the end of the peak effect phenomenon.
为了研究通过 Bridgman 技术制备的 Fe(Se, Te) 铁基超导体的超导和钉扎特性，我们进行了 DC 磁化 M 随磁场 (H) 和时间 (t) 的变化的测量。通过在垂直和平行磁场的情况下在不同温度下执行超导磁滞回线 M(H)，我们在 Bean 临界态模型的框架内提取了两种配置下的临界电流密度 J (H)。J (H) 曲线显示出存在第二磁化峰效应，这导致临界电流密度对磁场的依赖性异常增加。为了获得样品的 J 各向异性，我们执行了垂直和平行临界电流密度值的比值 [Formula: see text]，并将其与文献值进行了比较。通过在 H∣∣c 情况下不可逆磁化 M(t)的弛豫，我们提取了关于钉扎能 U 的信息。特别地，通过在不同温度和磁场下进行弛豫测量，我们获得了不同磁场下钉扎能 U(T)随温度的依赖性，显示出曲线的异常温度标度。U(T)曲线中存在最大值表明在给定磁场和温度 H (T)下存在钉扎交叉。H (T) 值符合方程 H (T) = H (0) (1 - T/T*)，其结果证实了弹性/塑性交叉和峰效应现象结束之间的相关性。
