Magnetic studies of flux pinning in YBa 2Cu 3O 7− x, YBa 2Cu 4O 8 and Hg-based single crystals

Abstract

The flux-pinning mechanism in YBa 2Cu 3O 7− x (Y-123), YBa 2Cu 4O 8 (Y-124), HgBa 2CuO 4+ x (Hg-1201) and HgBa 2Ca 2Cu 3O 8+ x (Hg-1223) is compared. Single crystals of Y-123, Y-124 and Hg-1201 show a very pronounced fishtail effect, observed in a wide temperature range. For each compound the irreversibility field and the field at which the peak in the fishtail occurs are well described by a power-law dependence H irr/peak(T) = H irr/peak(0)(1 − T/T c) α with very similar exponents. In Hg-1223 the pinning has a more three-dimensional character at higher temperatures, but becomes rather two dimensional at low temperatures.