Hysteresis of the magnetoresistance of granular HTSC YBa2Cu3O7 − δ in weak fields

Hysteresis of the magnetoresistance of ceramic YBa2Cu3O∼6.95 HTSC samples is studied at T = 77.3 K in an external magnetic field Hext changing in 0 → Hmax → 0 cycles, where Hmax is the maximum magnitude of Hext. Information is obtained about the dependences of the critical fields of Josephson weak links Hc2J, the lower critical fields of superconducting grains Hc1A, and the critical fields HBG-VG of the Bragg glass-vortex glass phase transition in the vortex matter on transport current I, magnetic field, and the mutual orientation of I and Hext. It is found that the magnetoresistance δρ+/ρ273 K measured with increasing Hext is significantly higher than Δρ−/ρ273 K and that Hc2J+ < Hc2J−, Hc1A+ < Hc1A−, and HBG-VG+ < HBG-VG−.