Preparation and magnetic properties of Re-doped HgBa2Ca2Cu3O8+delta superconductors

Nearly phase-pure (Hg1-xRe0.1)Ba2Ca2Cu3O8+delta superconducting specimens were prepared by a conventional powder-mixing and encapsulation technique. The magnetization M was measured for sintered bulk samples and for grain-aligned powders, and M is much larger for H parallel to c-axis than for H parallel to a-b plane. \M\ decreases sharply just above the penetration field H-p in the field-increasing branch. At high and moderate temperatures (T greater than or equal to 40 K), the remanent magnetization at H = 0 is small and the M-H curves are completely asymmetric about the central line of M = 0. These features clearly show that the magnetization originates from the Bean-Livingston surface barrier. Substantial bulk pinning exists only at low temperatures, T less than or equal to 20 K. The magnetic hysteresis curves of Re-doped Hg-oxide samples also exhibited paramagnetism, in which a Curie-Weiss behavior occurs above T-c. This paramagnetism is probably mainly carried by doped Re ions.