MAGNETIC-FIELD AND HIGH-PRESSURE DEPENDENCES OF T-C AND CRITICAL-CURRENT IN THE POLYCRYSTALLINE HGBACACUO SYSTEM

The high-temperature phase Hg0.8Pb0.2Ba2Ca2Cu3O8+delta (HBCCO) with th e onset transition temperature T-c approximate to 133 +/- 0.5 K has be en investigated under hydrostatic pressure up to 12 kbar. We found a p ositive pressure effect on T-c with a rate 0.28 +/- 0.04 K/kbar and a positive pressure effect on the transport critical current J(c), dln(J (c))/dP = 0.2 +/- 0.02 kbar(-1). The observation of a strong hysteresi s effect in the J(c) versus magnetic field H dependences shows the pos sibility of surface barriers to vortex motion in the high-T-c HBCCO sy stem.