Specific features in the hysteretic behavior of the magnetoresistance of granular high-temperature superconductors

The behavior of the hysteresis of the magnetoresistance $R(H)$ of granular high-temperature superconductors has been investigated under the conditions where the resistive response of the subsystem of grain boundaries close to saturation. The hysteretic dependences $R(H)$ have been measured for Y$_{1-x}$Pr$_x$Ba$_2$Cu$_3$O$_7$ samples at $x$ = 0.11 and 0.04 with the transition temperatures $T_C\approx$ 85.5 and 91.0 K, respectively. The evolution of the field width of the hysteresis $R(H)$ has been examined by varying the measuring current. The limit of the applicability has been established for the concept of the effective field in the intergranular medium, which was previously proposed for the description of the hysteretic behavior of the magnetoresistance $R(H)$ and thermal magnetic prehistory of the granular high-temperature superconductors. In the studied samples, the approximation of the effective field in the intergranular medium is applicable until the magnetoresistance of the subsystem of grain boundaries exceeds (90 $\pm$ 5)% of the maximum value.