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Systematic measurements of the AC magnetic susceptibility of polycrystalline RuSr2GdCu2O8 (Ru-1212) samples are reported for various frequencies and magnetic field amplitudes. The study covered frequency range from 22 Hz to 12.5 kHz and field amplitudes between 0.5 to 25 Gauss. Both of the susceptibility components χ', and χ'' are greatly affected by frequency and applied field depending on the relevant range under consideration.
In addition, the measured data of the susceptibility components were employed to extract inter- and intra-grain superconductive transition temperatures as well as the average transition temperature in magnetic superconductor RuSr2GdCu2O8. The intra- and inter-granular components of the granular susceptibility components were also estimated. It was found that both of the intra- and inter-granular transition temperatures increase by increasing field frequencies and decrease by increasing the field amplitudes. This might be an indication that the grains of RuSr2GdCu2O8 behave differently from a homogenous bulk superconductor. The nature of curves indicated the presence of a superconducting transition between grains, coupled by weak links with a distribution of critical temperatures, and the superconducting transition within the grains. The two transitions observed are linked to the typical intra- and intergrain transitions of a granular superconductor. The weak coupling between grains might be modeled in terms of Josephson-junction arrays.