Synthesis of (Hg,Re)Ba2Can−1CunO2+2n+δ (n = 2, 3, 4) single crystals and their magnetization properties

Single crystals of (Hg,Re)Ba2Can−1CunO2+2n+δ (n = 2, 3, 4) with size up to 1 × 1.1 × 0.1 mm3 were grown by the flux method in quartz ampoules from flux compositions with excess Ba and Cu. In order to synthesize high purity crystals without contamination from crucible materials, the BaZrO3 crucibles which are stable against molten Ba–Cu–O, were used. The obtained single crystals were of nearly carrier optimally doped state with Tcon=123, 131 and 125 K for crystals with n = 2, 3, 4, respectively. Broad second peaks were observed in their magnetization hysteresis loops in a wide temperature range, and therefore, the existence of effective field-induced pinning sites probably due to inhomogeneous distribution of rhenium was indicated. The behaviors of irreversibility lines as a function of reduced temperatures by Tc, T/Tc, of these crystals were almost identical independent of n   and their electromagnetic anisotropy parameter γ2(=mc∗/mab∗) were estimated to be 500–700.