For optimally doped high-temperature superconductors YBa2Cu3O6.92 with various degrees of structural inhomogeneity, the influence of this inhomogeneity on the manifestation of the Meissner effect is considered. The measurement results indicate that for the samples under study, for which almost identical superconducting transition Tс = 92K temperatures were realized, the Meissner effect values turned out to be different and correlated with the degree of structural inhomogeneity, which is also characteristic of other magnetic properties.

Структурные, магнитные и термодинамические свойства упорядоченного и разупорядоченного Sr 0.9 Gd 0.1 CoO 3-δ

AbstractA method for calculating the critical current of an inhomogeneous superconducting film (plate) in different external magnetic fields has been proposed. The superconducting properties are changed by varying the coherence length and London penetration depth over the thickness. The coherence length is maximum at the center of the plate and decreases upon approaching its boundaries and the London depth, on the contrary, is minimum at the center of the plate and increases toward its boundaries. Using the proposed approach, the magnetic field dependences of the critical current on the external magnetic field for the cases of nonuniform and uniform distributions of the superconducting properties over the film thickness have been calculated and compared. It has been established that at the nonuniform distribution of the superconducting properties the critical current of the plate is higher than at the uniform distribution at the same external magnetic fields. This is due to the fact that the order parameter is redistributed over the inhomogeneous plate thickness in such a way that the superconducting state becomes more stable against the current and magnetic field. It has been shown that the vortex-free Meissner state in inhomogeneous films is maintained at higher fields than in homogeneous films. The greater the film nonuniformity, the higher the stability of the Meissner state against an external magnetic field.

Методами вибрационной магнитометрии проведены исследования изменений электрофизических характеристик нескольких типов современных коммерческих многожильных композиционных проводов на основе сверхпроводящего соединения Nb3Sn при температурах 4.2, 7 и 12 K в магнитных полях до 8 T до и после облучения на циклотроне НИЦ КИ быстрыми протонами с энергией 32 MeV и флюенсами облучения phi t = 3 · 1016, 1· 1017, 3· 1017 и 1· 1018 cm-2. Для всех образцов при флюенсах облучения до phi t = 1 · 1017 cm-2 отмечен рост критической плотности тока, наиболее резко выраженный в сильных магнитных полях и при низких температурах; при флюенсе облучения phi t = 1 · 1018 cm-2 наблюдается падение критической плотности тока до уровня меньше исходного. Критическая температура образцов монотонно уменьшается с ростом флюенса облучения. DOI: 10.21883/PJTF.2017.12.44710.16495