Trapped Flux Behavior in Melt-Growth GdBCO Bulk Superconductor Under Off-Axis Field Cooled Magnetization

The effective pinning of magnetic flux in high-temperature superconductor bulk plays a basic role in a variety of engineering applications as superior magnetic field sources. We have studied the trapped magnetic flux behavior of large single-grain GdBa
₂
Cu
₃
O
_7-δ
(GdBCO) bulk cryomagnet. Here, an off-axis field cooled magnetization is proposed, in which magnetic field was applied with an angle θ with respect to the crystallographic c-axis of the bulk, i.e., off-axis geometry. To verify the trapped flux performance, the flux density parallel to the c-axis was scanned with Hall sensor on the surface of the bulk after off-axis field cooled magnetization. It was found that the trapped flux component along the c-axis still remains strong with up to θ = 30°, and the total flux over the bulk surface reaches over 97% compared with that when θ = 0°. These results demonstrate GdBCO bulk can nearly maintain their full trapped flux potential along the c-axis under off-axis field cooled magnetization with finite inclination angle. Thus, the present off-axis magnetization can provide an alternative choice for the magnetization geometry design in HTS applications using bulks, when the magnetizing field cannot be applied perfectly aligned with the crystallographic c-axis of the bulk.