Cuprate superconductors (RE)Ba₂Cu₃O₇(RE: Rare Earth, and it is called REBCO), which have higher critical current density than other superconductors at high temperatures and high fields, are expected to be used for superconducting cables and magnets. The commercially available REBCO coated conductors, which are thin tapes, can be cut and stacked to form a stacked magnet. To date, there have been many studies on stacked magnets because they can be applied for NMR, motor, etc. Our group fabricated a compact and high-field stacked magnet and succeeded in generating 13.6 T at 15 K [1].

In this study, we fabricated a stacked magnet using EuBCO coated conductor with BaHfO₃nanorods (Fujikura Ltd.), and aimed at obtaining better stacked magnet than our previous study. We improved the fabrication process so that the effect of cutting-induced damages in coated conductors becomes minimum and guarantee better thermal conductivity by applying stronger force from above. We have succeeded in magnetizing the stacked magnet at lower temperatures than the previous study and trapping 14.1 T of field at 10 K. In addition to this, we succeeded in trapping high magnetic fields in shorter times.

 We will discuss the comparison of the experimental results and calculated trapped field based on the realistic J_c-H characteristics. We will also show and discuss the result of crossed-filed demagnetization of the stacked magnet, which could be relevant when it is applied to motors [2].

[1] T. Hashimoto, master thesis, Department of Applied Physics, The University of Tokyo (2019).
[2] M. Baghdadi et al., Appl. Phys. Lett. 104, 232602 (2014).

Fig. Temperature dependences of trapped field in the present (2020) and the previous (2019) studies [1], measured at two positions near the center.

Keywords: REBCO, coated conductor, stacked magnet, trapped field