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Abstract <p>The present study investigates the dependences of the intragranular critical current density (<i>J</i><sub>c</sub>) and of the thermodynamic critical field (<i>H</i><sub>c</sub>) on the iron content (<i>x</i>) for samples with the composition Y<sub>1–<i>x</i></sub>Fe<sub><i>x</i></sub>Ba<sub>2</sub>Cu<sub>3</sub>O<sub><i>y</i></sub> (0 ≤ <i>x</i> ≤ 0.06). The dependences of <i>J</i><sub>c</sub><i>(x)</i> have a pronounced maximum at the optimum doping concentration, <i>x</i><sub>opt</sub> ~ 0.04, corresponding to the average distance of ~ 2 nm between magnetic defects. The higher <i>J</i><sub>c</sub> at <i>x ~ x</i><sub>opt</sub>, compared to the undoped sample, reaches two orders of magnitude in the external magnetic field, <i>H</i> = 1 T, at temperatures near 77 K. The value of <i>x</i><sub>opt</sub> weakly depends on <i>H</i> and temperature. At the same time, unlike the type of dependences of <i>J</i><sub>c</sub>(<i>x</i>), <i>H</i><sub>c</sub>&#xa0;decreases monotonically with increasing <i>x</i>. A model explanation of the obtained results is proposed, based on the existence of normal regions in the vicinity of the defect, whose size is of the order of coherence lengths. There is no shielding of iron-ion moments within these regions when the sample transitions to a superconducting state. The mechanism of magnetic pinning caused by the interaction between the magnetic moment of a defect and the heterogeneous vortex lattice field is examined.</p>

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Magnetic Pinning and Substantial Enhancement of Critical Current in Iron-Doped YBaCuO

  • 期刊论文

  • 发表日期：

    2025年12月1日

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  • K. S. Pigalskiy,
  • A. A. Vishnev,
  • N. N. Efimov,
  • P. N. Vasilyev,
  • A. V. Shabatin,
  • L. I. Trakhtenberg

摘要

Abstract

The present study investigates the dependences of the intragranular critical current density (Jc) and of the thermodynamic critical field (Hc) on the iron content (x) for samples with the composition Y1–xFexBa2Cu3Oy (0 ≤ x ≤ 0.06). The dependences of Jc(x) have a pronounced maximum at the optimum doping concentration, xopt ~ 0.04, corresponding to the average distance of ~ 2 nm between magnetic defects. The higher Jc at x ~ xopt, compared to the undoped sample, reaches two orders of magnitude in the external magnetic field, H = 1 T, at temperatures near 77 K. The value of xopt weakly depends on H and temperature. At the same time, unlike the type of dependences of Jc(x), Hc decreases monotonically with increasing x. A model explanation of the obtained results is proposed, based on the existence of normal regions in the vicinity of the defect, whose size is of the order of coherence lengths. There is no shielding of iron-ion moments within these regions when the sample transitions to a superconducting state. The mechanism of magnetic pinning caused by the interaction between the magnetic moment of a defect and the heterogeneous vortex lattice field is examined.