  The value of a locally frozen magnetic field in a region with a diameter of
0.5 mm in a 0.5-mm-thick YBa2Cu3O7-x plate was investigated as a function of
the excitation field (to 2x10^4 A/m), plate cooling mode (in the absence or
presence of a field; i.e., zero-field cooling (ZFC) or field coupling (FC)),
and local demagnetizing field. Analysis of the measurement results in the noted
range of excitation fields showed the following: (i) the dependence on the
excitation field for the ZFC mode is explained by the local inhomogeneity of
critical currents of weak links in the ceramic Josephson medium and is limited
by their maximum value at the temperature of the experiment (77 K); (ii) the
dependence on the excitation field for the FC mode contains a portion of the
magnetic phase transition from the frozen current structure, typical of the
initial portion of the dependence, to the current structure characteristic of
the ZFC freezing mode, and is limited by this transition; and (iii) the
dependence on the demagnetizing field for the ZFC mode can be explained by the
stable coexistence (without annihilation) of microscopic current loops with
opposite current directions in the ceramics.
