CRITICAL-CURRENT DENSITY AND ACTIVATION-ENERGY IN MELT-TEXTURED GROWTH YBACUO FROM MAGNETIC MEASUREMENTS

Textured YBaCuO samples have been prepared using a modified melt textured growth (MTG) method. AC susceptibility data are presented showing the high quality of the textured samples. Static hysteresis loop measurements are realized for magnetic fields up to 5 T in a large temperature range (4.2 to 100 K). The anisotropic behavior is studied, the magnetic field being applied successively in the (ab) planes and along the c-axis. The critical current densities are obtained using the Bean model. Dynamic hysteresis loop measurements are performed at T greater-than-or-equal-to 77 K and over the frequency range from 0.2 to 10 Hz using a field of 800 Oe. The magnetization relaxation effect appears to be significantly lower in the textured sample than in a single crystal. The characteristic activation energies calculated in the flux creep model are presented.