Effect of hydrostatic pressure on HgBa2Ca2Cu3O8+delta superconductor dopedwith Re

Samples of the Hg1-xRexBa2Ca2Cu3O8+delta superconductor (Hg, Re-1223), with varying rhenium (Re) content (0.00<x<0.30) were produced with the help of a thermobaric analysis, which can monitor the total pressure inside the qua rtz tube during the synthesis at high temperatures. The sample quality was verified by means of Rietveld analysis of the x-ray-diffraction data, ac su sceptibility, and by ac resistance measurements. The same procedure was use d to prepare all the samples with different Re content (reduction of oxygen content in the precursor RexBa2Ca2Cu3O7+ delta and the increase of the mer cury partial pressure inside the quartz tube). The Re atoms lead to a reduc tion of the lattice parameter along the c axis with a decrease of the latti ce volume which is equivalent to an applied hydrostatic pressure of 1 GPa. The aim of this work is a comparative and quantitative study of the chemica l and external hydrostatic pressure on the Hg, Re-1223 system. The samples with 0.10<x<0.25 showed strong magnetic shielding effects and low residual resistance. Resistance measurements as a function of temperature display an increase of the superconducting transition temperature Te with applied hyd rostatic pressure. The partial derivative T-C/partial derivative P value de pends strongly on the Re doping and the sample with the Re content x=0.18 s howed the largest measured partial derivative T-C/dP = 6.8(2) K/GPa. We arg ue that the Re concentration does not increase Te in the same way as extern al hydrostatic pressure but provides a strong influence on the intrinsic te rm proposed by Almasan et al. [Phys. Rev. Lett. 69, 680 (1992)].