We measured the trapped field profiles on a
∅45 mm GdBCO superconducting bulk plate of 2 mm thickness magnetised
using pulsed field magnetisation (PFM), zero-field-cooled magnetisation
(ZFC) and field-cooled magnetisation (FCM). The profiles were compared
with the distribution of the absolute value of the critical current density (Jc)
estimated by the magnetisation measurements using small pieces cut from the bulk plate. The
Jc value
was enhanced about 20% below the seed crystal compared with that in the growth sector regions (GSRs).
The Jc
value was also slightly enhanced on the growth sector boundaries (GSBs).
For a lower applied pulsed field than that for full magnetisation for PFM, a
small amount of the magnetic flux was preferentially trapped at the lower
Jc
region around the bulk periphery, which was not necessarily similar to that by ZFC. For a
higher applied pulsed field, the magnetic flux was finally trapped below the seed crystal
and at the GSBs.
Square GdBaCuO bulks with 45.2 ×45.2 mm2 in the a
b-plane and 15 mm in thickness along the c-axis with different arrangements of growth sector boundaries (GSBs) were magnetized by a field-cooled magnetization (FCM), a zero-field cooled magnetization (ZFC), and a pulsed-field magnetization (PFM) and the trapped field profiles were measured. For the lower applied field in ZFC, the magnetic flux was trapped in the growth sector regions (GSRs), independent of the arrangement of GSBs. For the lower applied field in PFM, the magnetic flux was mainly trapped in the GSRs and an additional flux was also trapped at the sides in both bulks because of the complicated flux intrusion by the local heat generation. These bulks can trap a magnetic field as high as 7.5 T at 50 K by FCM without destruction. The magnetic flux intrusion and trapping for the square bulks were discussed.
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