Mössbauer and magnetic studies of bulk and fine-powder SrRu O3 and Sr-Cu-Ru O3 systems

SrRu O3 is a ferromagnet, TC =165 K. Due to difference in grain sizes, ceramic bulk and fine-powder (prepared by the sol-gel procedure) of SrRu O3, have different coercive fields. The Fe57 doped Mössbauer effect spectra (MS) of powder SrRu O3 exhibit distinct magnetic hyperfine sextets up to TC, while none is observed at 90 K in the bulk material. This is probably a result of the fact that the Fe57 probe resides in the Sr and Ru sites for powder and bulk SrRu O3, respectively. Due to the shorter Sr-Ru distance, the Fe57 ions in the Sr site are exposed to an exchange field from the Ru magnetically ordered ions, much more than the iron in the Ru site. The Fe57 MS spectra of Sr1-x Cux Ru O3 and Sr Ru1-y Cuy O3 systems behave similarly to powder and bulk SrRu O3, respectively. The magnetic properties of the two systems are discussed. The above results served as the basic explanation for the peculiar magnetic behavior of the magneto superconducting Ru Eu1.5 Ce0.5 Sr2 Cu2 O10 in the temperature range 90-165 K.