Flux pinning and the irreversibility line in the grain aligned HgBa 2Ca 2Cu 3O y superconductor

Abstract

From magnetization studies for the grain aligned HgBa 2Ca 2Cu 3O y superconductor the temperature variation of critical current density J c ( T) values was characterized by an exponential decay of the form J c ∝exp ( −T T 0 ). Flux pinning was significantly greater with the peak F p, 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 ∝ (1 − T T c ) n with n = 1.7 at T > 80 K. Thus, we obtained the result that the pinning potential U(H) ∝ H −1 4.6 at T < 80 K and F p, max ∝ H irr α with the exponent α = 0.8. From flux-pining diagram of the vortex state, we found that the SVP (single vortex pinning) regime is extended up to 60 K.