1 1 Ja n 19 99 Coexistence of ferromagnetism and superconductivity in the hybrid ruthenate - cuprate compound

Coexistence of ferromagnetism and superconductivity in the hybrid ruthenate-cuprate compound RuSr 2 GdCu 2 O 8 studied by muon spin rotation (µSR) and DC-magnetization Abstract We have investigated the magnetic and the superconducting properties of the hybrid ruthenate-cuprate compound RuSr 2 GdCu 2 O 8 by means of zero-field muon spin rotation-(ZF-µSR) and DC magnetization measurements. The DC-magnetisation data establish that this material exhibits ferromagnetic order of the Ru-moments (µ(Ru) ≈ 1 µ B) below T Curie = 133 K and becomes superconducting at a much lower temperature T c = 16 K. The ZF-µSR experiments indicate that the ferromagnetic phase is homogeneous on a microscopic scale and accounts for most of the sample volume. They also suggest that the magnetic order is not significantly modified at the onset of superconductivity.