We report on magnetic, resistivity, Mössbauer spectroscopy, and scanning tunneling spectroscopy studies of ceramic superconducting (SC) and non-SC $\mathrm{Ru}{\mathrm{Sr}}_2{\mathrm{Y}}_{1.5}{\mathrm{Ce}}_{0.5}{\mathrm{Cu}}_2{\mathrm{O}}_{10-\delta }$ $(x=0.5)$ and $\mathrm{Ru}{\mathrm{Sr}}_2\mathrm{Y}\mathrm{Ce}{\mathrm{Cu}}_2{\mathrm{O}}_{10}$ $(x=1)$. All materials studied were prepared at high oxygen pressure under the same conditions. Two magnetic transitions at $T_{2\mathrm{M}}$ and $T_{\mathrm{M}}$ $(T_{2\mathrm{M}}<T_{\mathrm{M}})$ are observed. For the SC $x=0.5$ material, both $T_{2\mathrm{M}}$ and $T_{\mathrm{M}}$ and saturation moments are lower, but its coercive fields are higher as compared to the non-SC $x=0.5$ sample material. In the $x=1$ sample, a dramatic increase in the magnetoresistance occurs at $T_{\mathrm{M}}$.

• Received 2 July 2007

DOI:https://doi.org/10.1103/PhysRevB.76.144514