Transport and microwave study of superconducting and magnetic RuSr2EuCu2O8- art. no. 064508

We have performed susceptibility, thermopower, dc resistance, and microwave measurements on RuSr2EuCu2O8. This compound has recently been shown to dis play the coexistence of both superconducting and magnetic order. We find cl ear evidence of changes in the dc and microwave resistance near the magneti c ordering temperature (132 K). The intergranular effects were separated fr om the intragranular effects by performing microwave measurements on a sint ered ceramic sample as well as on a powder sample dispersed in an epoxy res in. We show that the data can be interpreted in terms of the normal-state r esistivity being dominated by the CuO2 layers with exchange coupling to the Ru moments in the RuO2 layers. Furthermore, most of the normal-state semic onductorlike upturn in the microwave resistance is found to arise from inte rgranular transport. The data in the superconducting state can be consisten tly interpreted in terms of intergranular weak links and an intragranular s pontaneous vortex phase due to the ferromagnetic component of the magnetiza tion arising from the RuO2 planes.