Magnetic field and temperature dependence of the intergranular activation energy in a polycrystalline HgBa2Ca2Cu3O8+delta superconductor

The AC susceptibilities of a polycrystalline HgBa2Ca2Cu3O8+delta sample were measured as a function of temperature, magnetic field and frequency. The activation energy, obtained from an Arrhenius plot for the frequency f and the maximum temperature T-p in the imaginary part chi '' of the AC susceptibility, was approximated by U(H,T) approximate to A(1 - T/T-c)H-0.15 for temperature and field. The maximum field H-p in the imaginary part chi '' exhibited the power-law dependence (1 - T/T-c)(5) for the temperature range near T-c. (C) 1997 Elsevier Science B.V.