Magnetoresistance of granular YBa2Cu3O7-δHTSC in weak magnetic field:: Angular dependence

The magnetoresistance of ceramic YBa2Cu3O similar to 6.5 HTSC samples is studied as a function of the mutual orientation of the current I and external magnetic field H-ext at T = 77.3 K in magnetic fields of up to similar to 500 Oe. It is found that, if the demagnetization factor D is taken into account, the effective critical field of complete penetration of Josephson vortices into weak links H (eff)(c2J) does not depend on the mutual orientation of I and H-ext. The lower critical field H-c1A(eff) associated with the beginning of penetration of Abrikosov vortices into superconducting grains increases substantially with the angle between I and H-ext. The strongest variation with the mutual orientation of I and H-ext is exhibited by the critical field of the Bragg glass-vortex glass first-order phase transition H-BG-VG(eff) and by the magnetoresistance jump at this phase transition.