We have measured trapped field distributions by scanning a Hall probe
on various rectangular YBCO bulk superconductors and studied the effec
ts of field dependence of J(c) bulk thickness and bulk size on the tra
pped field. The trapped field could be increased by increasing the bul
k thickness and size. However, a saturation was observed for the maxim
um thickness. We also calculated the distribution of trapped field tak
ing account of the field dependence of J(c). Experimental trapped fiel
d distributions were in good agreement with our calculated values when
we used the J(c)-B curves obtained from a d.c. magnetization measurem
ent for samples. (C) 1997 Published by Elsevier Science Ltd.