Two Mixed Superconducting Phases in (Hg,Re)-1223 Ceramics

We investigate Hg _0.82Re _0.18Ba ₂Ca ₂Cu ₃O _8.76 polycrystalline samples with an optimum oxygen content aimed to analyze both their granular composition and to measure their magnetic response. We find out that the sample corresponds to a solid solution of two intrinsic structural superconductor phases. The AC magnetic susceptibility of a powder sample with a particle size of 20 μm have a critical temperature at 133 K. To make mesoscopic-scale particles of 600 nm in size, a sample of the powder was crushed and sieved. Now, the AC magnetic sample susceptibility shows two critical temperatures at 133 and 98 K. They have been described adopting a particular parametrization of the complex scalar field associated with the order parameter in a new framework of the Ginzburg–Landau theory. Thus, we propose a microscopic model to describe the dynamical interaction between these two types of grains.