  The properties of a locally frozen (in a region of diameter 0.5 mm) magnetic
field in a YBa2Cu3O7-x slab 0.5 mm thick are investigated as a function of the
value of the excitation field, the regime of freezing, and the transport
current through the sample. The first regime is cooling of the ceramic to 77 K
in the excitation field with a subsequent turning off of the excitation field,
and the second regime is cooling in the Earth's magnetic field with a
subsequent turning on and off of the excitation field. At an excitation field
up to 2000 A/m in these regimes two different types of macroscopic current
vortex structures, which generate the frozen field, are formed. The local
critical field of excitation when the vortex structure is formed in the second
regime exceeds the uniform perpendicular critical field of the slab by a factor
of 10 and equals 1700 A/m. On the other hand, the vortex structure of the first
type can be formed by practically any weak excitation field, including fields
smaller than the critical field of the vortex structure of the second type. In
a representation of the ceramic as a Josephson medium, physical models of the
two types of vortex structures are proposed which correspond most fully to the
results of experiments. The displacement of the vortex structure of the first
type upon the passage of transport current through the slab, as a result of the
action of the Lorentz force on that structure, is registered. This makes it
possible to calculate the pinning force Fp and to estimate the value of the
viscosity n for the motion of such a vortex structure in the ceramic: Fp=6x10-8
N, n =6x10-5 kg/s.
