The irreversibility line of HgBa2CuO4+δ

Abstract
Using magnetization hysteresis loops we have determined the irreversibility line of polycrystalline samples of HgBa2CuO4+δ and Hg0.8Pb0.2Ba2CuO4+δ. The irreversibility line is found at rather high temperatures. It does not show the drastic depression with increasing temperature as is observed in highly anisotropic Bi/Tl-based CuO superconductors. At 77 K the irreversibility field is around 0.3 T, which is substantially higher than in Bi2Sr 2CaCu2O8 and Bi2Sr 2Ca2Cu3O10. The advantages of this material for large-scale applications are outlined