High magnetic field trapping in monolithic single-grain YBa ₂Cu₃O_7-δbulk materials

Results of our study on high magnetic field trapping in unirradiated, high quality monolithic single-grain YBa₂Cu₃O _7-δ disks are reported. A record high 4 T trapped field at the surface of the unirradiated disks is observed. However, below 11 K, large flux avalanches caused by thermal instability severely limit the remnant trapped field. Therefore, flux avalanche, rather than J_c×d, dictates the maximum trapped field at low temperatures. To overcome this problem, a strong high temperature superconductor trapped field magnet is proposed. A novel application of the avalanche effect is also mentioned.