Thermal fluctuation in high-temperature superconductor HgBa₂CaCu₂O_6+δ

The reversible magnetization M has been carefully measured on a polycrystalline HgBa₂CaCu₂O_6+δ sample (Hg-1212), with a superconducting transition temperature T_c{reversed tilde}119 K and a transition width ΔT{reversed tilde}2 K. The magnetization is field independent at 116 K, suggesting a significant role of thermal fluctuations. The value of this magnetization leads to an estimated superconducting volume fraction of 65% based on a quasi-2D thermal fluctuation model. After corrections for fluctuation and random grain orientation, the superconducting parameters of κ{reversed tilde}60, H_c2(0) {reversed tilde} 53 T, ξ_ab(0) {reversed tilde} 25 Å, and λ_ab(0) {reversed tilde} 1500 Å are obtained.