Field Dependence Of Penetration Depth Research Articles

Critical Current and Flux Pinning Characteristics in Sr0.6K0.4Fe2As2 Superconducting Tapes

Since novel iron-based pnictide of Sr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.6</sub> K <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.4</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> As <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> superconductor was discovered, the applications on high magnetic field and large current transportation are highly expected due to its low cost and unique superconductivity such as low anisotropy, relatively high critical current density, and critical temperature. Recently, we have successfully developed the Fe-clad superconducting Sr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.6</sub> K <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.4</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> As <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> tape with the critical temperature of 32.5 K and fairly high critical current density of 1.5×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">8</sup> A/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> at 10 T and 4.2 K. Since the critical current density is considered as one of the most important factors for applications of superconducting materials, detailed investigation on the critical current characteristic and flux pinning mechanism in the supposed operation temperature range is necessary. In this paper, the critical current densities in the temperature range of about 20 K-30 K and at the magnetic field of up to 7 T were measured by using an inductive method (Campbell's method). It turned out that the critical current density of the tape is fairly high around 20 K. In this paper, basing on the experimental results of the penetrating ac magnetic flux profile and the feature of ac magnetic field dependence of penetration depth, the flux pinning mechanism of the sample was discussed.

Magnetic Field Dependence of Penetration Depth in Kinetic Energy Driven Cuprate Superconductors

Within the kinetic energy driven superconductivity, the magnetic field dependent penetration depth in cuprate superconductors is studied in the linear response approach. The electromagnetic response kernel is evaluated by considering both couplings of the electron charge and electron magnetic momentum with a weak magnetic field and employed to calculate the penetration depth based on the specular reflection model, then the main features of the magnetic field dependent penetration depth are well reproduced.

Magnetic Field Dependence of Penetration Depth of Optimally Doped Bi2Sr2CaCu2O8+? Single Crystal

The behavior of the in-plane penetration depth λ(T) extracted from the reversible magnetization in different magnetic fields for Bi2Sr2CaCu2O8+δ single crystal is investigated. It is found that the temperature dependence of penetration depth in different fields follows a quadratic function between 40 and 60 K. The magnetic field dependence of penetration depth at different temperatures obeys a power law. The observed temperature dependence of λ(T) in different fields is similar to the predicted behaviors of the nonlocal-nonlinear London theory.