Temperature dependence of the resistivity of the Y-Ba-Cu-O superconducting films
Garin F. V. , Kochemasov A. V., Strikovskii M. D., Mel'nikov A. S. , Sharov S. V.
If the volume of a high-temperature superconductor is divided into grains whose boundaries are Josephson junctions, the Meissner state will be disrupted in a very weak field Hci —weaker than the field of the earth. The experimental values of the lower critical field, which are significantly higher than this value, should be associated with another critical field, Ηί, at which vortices begin to penetrate into the volume of the grains.