QUASIPERMANENT MAGNETS OF HIGH-TEMPERATURE SUPERCONDUCTOR - TEMPERATURE-DEPENDENCE

We report on persistent field in quasipermanent magnets of high temperature superconductors. Magnets composed of irradiated Y1+Ba2Cu3O7 trapped field B(t) = 1.52 T at 77 K and 1.9 T at lower temperature. However, the activation magnet limited B(t) at lower temperature. We present data on J(c)(HT) for unirradiated materials, and calculate B(t) at various T. Based upon data at 65 K we calculate B(t) in unirradiated single grains at 20 K, and find that 5.2 T will be trapped for grain diameter d approximately 1.2 cm, and 7.9 T for d=2.3 cm. Irradiated grains will trap four times these values.