Inhomogeneous distribution of the pinning force in superconductor results in a magnetization asymmetry. A model considering the field distribution in superconductor was developed and symmetric and asymmetric magnetization loops of porous and textured Bi1.8Pb0.3Sr1.9Ca2Cu3Ox were fitted. It is found that the thermal equilibrium magnetization realizes in crystals smaller than some size depending on temperature and magnetic field.

Magnetization asymmetry of type-II superconductors in high magnetic fields

Inhomogeneous distribution of the pinning force in superconductor results in a magnetization asymmetry. A model considering the field distribution in superconductor was developed and symmetric and asymmetric magnetization loops of porous and textured Bi_{1.8}Pb_{0.3}Sr_{1.9}Ca_{2}Cu_{3}O_{x} were fitted. It is found that the thermal equilibrium magnetization realizes in crystals smaller than some size depending on temperature and magnetic field.

An extended critical state model has been developed. The model has considered the equilibrium magnetization of a surface layer and the magnetization of the central region of a superconducting sample. The magnetic flux distributions in the sample have been calculated. An analytical dependence of the critical cur� rent density on the magnetic field with different behaviors in strong and weak fields has been proposed. A rela� tion of the asymmetry of the magnetization loops and the critical current density to the sample size has been established. The model is applicable to the parameterization of magnetization loops of singlecrystal and polycrystalline superconductors.

An extended critical state model: Asymmetric magnetization loops and field dependence of the critical current of superconductors

The magnetization of porous Bi 1.8 Pb 0.3 Sr 2 Ca 2 Cu 3 O x has been investigated. The experimental magnetization hysteretic loops of M ( H ) were described in the frames of Val’kov–Khrustalev model developed for type II granular superconductors.

Magnetization loop and critical current of porous Bi-based HTS

Porous high-Tc superconducting materials offer several important benefits as compared to standard-type samples including an easy scalability towards large sample sizes, an easier oxygenation process and reduced weight. Due to these advantages, several different approaches to develop such samples were carried out in the literature. In this contribution, we present the microstructures and the physical properties of superconducting foams of YBa2Cu3O7 and fabric-like, nanowire networks of Bi2Sr2CaCu2O8. Further, we discuss the properties of such samples concerning both the physical parameters and the respective microstructures and give an overview about possible applications.

Porous high- T c superconductors and their applications

Preliminary data on the synthesis and physical properties of polycrystalline Bi1.8Pb0.3 Sr2Ca2Cu3Ox high-temperature superconductors of low density with a foam-like microstructure are reported.

T. N. Tetyueva

Papers

Synthesis, microstructure, and the transport and magnetic properties of Bi-containing high-temperature superconductors with a porous structure