Correlation Between Magnetoresistance and Magnetization Hysteresis in a Granular High-T_C Superconductor: Impact of Flux Compression in the Intergrain Medium

摘要

The correlation between experimental magnetic field dependences of magnetoresistance and magnetization hysteresis in granular YBa_2Cu_3O_7 is established. Within the proposed approach, magnetoresistance is assumed to be determined by the effective field in the intergrain boundaries the ensemble of which is considered to be a Josephson medium. The effective field in the intergrain medium can be written in the form B_(eff)(H) = H - 4πM(H) × α, where a is the parameter of averaged demagnetizing factors of grains and the degree of flux compression. A comparison of experimental magnetoresistance R (H) and magnetization M(H) hysteresis dependences obtained at different external magnetic field sweep rates yields the value α ～ 10, which is caused by the flux compression between grains. The proposed model describes well most of the features of the magnetoresistance hysteresis in granular high-T_C superconductors.