Possible phase separated bulk superconductivity in Ru0.9Sr2YCu2.1O7.9

The Ru0.9Sr2YCu2.1O7.9 sample being synthesized by high-pressure high-temperature solid-state reaction underwent (weak) ferromagnetic transition at 150 K followed by superconducting transition at 30 K. It showed clear Meissner signal in the field-cooled process up to external magnetic field of a few hundred Oe (~300 Oe). The magnetic susceptibility data and magnetic hysteresis data could be explained assuming that the sample was a macroscopic mixture of a superconductor and a (weak) ferromagnet. Any anomalous behaviour implying the coexistence of superconductivity and magnetism on a microscopic scale was not observed.