Compression of a magnetic flux in the intergrain medium of a YBa 2Cu3O7 granular superconductor from magnetic and magnetoresistive measurements

Abstract

A method to determine a value of the effective field in the intergrain medium of a granular superconductor is proposed. The space between superconducting grains is considered to be a Josephson medium where passage of the transport current causes dissipation and the effective field is superposition of external field H and the field induced by magnetic moments of superconducting grains. The method proposed is based on the comparison of hysteresis field dependences of magnetoresistance and magnetization and their relaxation at H const. By the example of granular YBa2Cu 3O7, it is shown that, in the region of weak fields, the effective field in the intergrain medium exceeds by far the external field, i.e., compression of a magnetic flux occurs. © 2011 American Institute of Physics.