Pulsed field magnetization of a 36 mm diameter single-domain Sm–Ba–Cu–O bulksuperconductor at 30, 35 and 77 K

Abstract

A c-axis oriented single-domain Sm–Ba–Cu–O bulk superconductor 36 mm in diameterwas magnetized by the pulsed field magnetization (PFM) method at 30, 35 and77 K. The trapped field distributions after applying pulsed fields with differentamplitudes were measured by scanning a Hall sensor 0.5 mm above the surfaceof the sample. We also measured the time evolution of magnetic fields duringthe PFM by using an oscilloscope connected to two Hall sensors mounted onthe bulk superconductor surface. Fluxes are found to penetrate into the bulksuperconductor and to escape from it by choosing passes through the direction inclined at45° to growth sector boundaries (GSBs) of the sample. At 35 K, the temperature rise of thesample caused by heat generation due to flux motion becomes more substantial than thatat 77 K. Thus, flux jumps occurred through the passes and assisted magnetic fluxesto reach rather easily the centre of the bulk superconductor. As a result, themagnetic field necessary for PFM is lower than that to fully magnetize the sampleby means of the static zero-field-cooling magnetization method. The optimizedmulti-PFM with reducing amplitudes, which was specifically referred to as theIMRA technique, turned out to be very effective in achieving excellent trappedfield characteristics by PFM at low temperatures. We could achieve a maximumtrapped field of 3.6 T together with a well conical trapped field distribution at 30 K.