Flux pinning and the irreversibility line in the grain aligned HgBa2Ca2Cu3Oy superconductor.

From magnetization studies for the grain aligned HgBa2Ca2Cu3Oy superconductor the temperature variation of critical current density J(c)(T) values was characterized by an exponential decay of the form J(c) proportional to exp(-T/T-0). Flux pinning was significantly greater with the peak F-p,F-max(T) shifted to higher magnetic field as decreasing temperature. For irreversibility line H-irr(T), the data could be fitted with the power law of T--m with m = 4.6 at T < 80 K and the scaling law of H-irr proportional to (1-T/T-c)(n) with n = 1.7 at T > 80 K. Thus, we obtained the result that the pinning potential U(H) proportional to H--1/4.6 at T < 80 K and F-p,F-max proportional to H-irr(alpha) with the exponent p, max alpha = 0.8. From flux-pinning diagram of the vortex state, we found that the SVP (single vortex pinning) regime is extended up to 60 K. Copyright (C) 1996 Elsevier Science Ltd