MAGNETIC-PROPERTIES OF THE HGBA2CA3CU4O10+DELTA SUPERCONDUCTING PHASE

The irreversible behavior of the HgBa2Ca3Cu4O10+delta phase was studied using DC magnetization measurements. The irreversibility line can be represented by the law H-irr = (1 - T-irr/T-c)(n) between 0.1 T and 5.5 T with a n value of about 3.2. The critical current densities obtained from the magnetic hysteresis using Bean's model were studied at high fields, showing a rapid decay with increasing field or temperature. An exponential decay of the form exp(T/T-0) for temperatures above 30 K was found, with a characteristic temperature T-0 = 7.2 K. A scaling behavior of the pinning forces was observed in the temperature range 60 < T < 75 K.