High Pinning Force Values of a Fe(Se, Te) Single Crystal Presenting a Second Magnetization Peak Phenomenon

The magnetization M of an Fe(Se, Te) single crystal has been measured as a function of temperature T and dc magnetic field H. The sample properties have been analyzed in the case of a magnetic field parallel to its largest face H||ab. From the M(T) measurement, the Tc of the sample and a magnetic background have been revealed. The superconducting hysteresis loops M(H) were between 2.5 K and 15 K showing a tilt due to the presence of a magnetic signal measured at T > Tc. From the M(H) curves, the critical current density Jc(H) has been extracted at different temperatures showing the presence of a second magnetization peak phenomenon. By extracting and fitting the Jc(T) curves at different fields, a pinning regime crossover has been identified and shown to be responsible for the origin of the second magnetization peak phenomenon. Then, the different kinds of pinning centers of the sample were investigated by means of Dew-Hughes analysis, showing that the pinning mechanism in the sample can be described in the framework of the collective pinning theory. Finally, the values of the pinning force density have been calculated at different temperatures and compared with the literature in order to understand if the sample is promising for high-current and high-power applications.

Investigation of Pinning Force Density Fp and Critical Current Density Jc of Nd0.33Eu0.33Gd0.33Ba2Cu3Oy(NEG-123) Superconductors with Addition of 211 Phase Particles and Analysis with a Theoretical Evaluation Based on Flux Creep-Flow Model

The pinning force density Fp and the critical current density Jc were investigated in Nd0.33Eu0.33Gd0.33Ba2Cu3O(NEG-123) superconductors with addition of NEG-211 and EG-211 secondary phase particles of the volume fractions up to 10 mol% by analyzing experimental data of DC magnetization and compared with theoretical calculation based on flux creep-flow model taking the pinning parameter into account. The pinning parameters such that the number of flux lines in the flux bundle (g2), the most probable value of pinning strength (Am), distribution width (σ2), upper critical field (Bc2) were determined so that a good fit was obtained between theoretical and experimental results. The Chittagong Univ. J. Sci. 42(1): 24-38, 2020