Flux pinning in HgBa2Ca2Cu3O8+x single crystals

Single crystals of HgBa2Ca2Cu3O8+x, with T-c onset = 120 K, were grown using a gas high pressure system. Magnetization studies were performed in a wide range of temperature and in magnetic fields up to 5 T using a dc SQUID magnetometer. The irreversibility line was determined from the magnetization measurements. On a log(H-irr) versus log(1 - T-irr/T-c) plot the irreversibility line shows two slopes. At higher temperatures the irreversibility line has rather three-dimensional character, whereas at lower temperatures the irreversibility line exhibits two-dimensional character.