Trapped field over 4 tesla on GdBaCuO bulk by pulse field method and magnetizing mechanism

We report a new pulse field magnetizing (PFM) method using the modified multi pulse technique combined with a stepwise cooling (MMPSC) to obtain the trapped field B_T^P over 4 T on a bulk superconductor. The B_T^P value as high as 4.47 T has been attained on the surface of the GdBaCuO bulk, which is the present highest using PFM. The key points to obtain the higher B_T^P are the introduction of a small amount magnetic flux (B_T^P∼1 T) into the bulk with the M-shaped trapped field distribution at a higher starting temperature T_s∼45 K, and the following application of the optimum stronger pulse fields of B_ex∼6.7 T at a lower T_s∼30 K. The reduction in the temperature rise ΔT due to the already existing trapped flux is a very important issue.