Superconductivity and magnetism in pure and substituted RuSr2GdCu8O8

We describe results of several macroscopic and local measurements of magnetic and superconducting properties for pure and Cc and Cu substituted RuSr2GdCu2O8. From various experiments the physical properties phase diagram is derived as a function of the hole doping. We show that the large contribution of polarized Gd3+ magnetic moments to magnetization causes apparent absence of the Meissner state and augments the weak Ru ferromagnetism. This weak ferromagnetism in the superconducting state can be significantly enhanced by the external magnetic field. These results indicate that the low-temperature behavior can be qualitatively explained assuming a quasi-two-dimensional character of the superconducting regions.