  The intrinsic pinning in high-temperature superconductor with long range
antiferromagnetic order of rare-earth ions confined to the isolating planes is
described. The interaction of antiferromagnetic and superconducting subsystems
in the mixed state may lead to the creation of spin-flop domain along the
vortex core. It is shown that the behavior of several physical quantities such
as magnetization, activation energy, current-voltage characteristic and flux
creep changes when the direction of the external field changes in the basal a-b
plane. It is also shown that the decay of the trapped flux is logarithmic
function of time
