Complex permeability of granular textured YBa2Cu2O7−δ superconducting ceramic

Abstract

Measurements of the complex permeability of the granular textured YBa2Cu3O7−δ ceramic as a function of the temperature in a weak ac magnetic field in the presence of a constant magnetic field have been performed. The experimental ceramic consisted of ∼3mm macrograins which formed in the process of texturization. The orientation of the c axis of the macrograins was chaotically distributed. A three-peak structure of the absorption of the ac magnetic field was observed in the imaginary part of the complex permeability in a weak constant magnetic field ∼0.1T. The behavior of this absorption structure as a function of the magnitude and orientation of the constant magnetic field, frequency, and amplitude of the ac magnetic field is analyzed. It is shown that the three-peak absorption structure in the imaginary part of the complex permeability is due to the influence of two mechanisms of the dissipation of the ac magnetic field energy: volume energy dissipation associated with pinning and surface energy dissipation associated with a Bean-Livingston surface barrier. It is found that as the constant magnetic field increases, this three-peak absorption structure transforms into a single-peak structure, described well in a linear model of thermally activated flow of magnetic flux.