Microwave and magnetotransport properties ofRuSr2RCu2O8(R=Eu,Gd)doped with Sn

${\text{Ru}}_{1\ensuremath{-}x}{\text{Sn}}_{x}{\text{Sr}}_{2}{\text{EuCu}}_{2}{\text{O}}_{8}$ and ${\text{Ru}}_{1\ensuremath{-}x}{\text{Sn}}_{x}{\text{Sr}}_{2}{\text{GdCu}}_{2}{\text{O}}_{8}$ have been comprehensively studied by microwave and dc resistivity and magnetoresistivity and by the Hall measurements. The ruthenium magnetic ordering temperature ${T}_{m}$ is considerably reduced with increasing Sn content. However, doping with Sn leads to only slight reduction of the superconducting critical temperature ${T}_{c}$ accompanied with the increase in the upper critical field ${B}_{c2}$, indicating an increased disorder in the system and a reduced scattering length of the conducting holes in ${\text{CuO}}_{2}$ layers. In spite of the increased scattering rate, the normal state resistivity and the Hall resistivity are reduced with respect to the pure compound, due to the increased number of itinerant holes in ${\text{CuO}}_{2}$ layers, which represent the main conductivity channel. Most of the electrons in ${\text{RuO}}_{2}$ layers are presumably localized, but the observed negative magnetoresistance and the extraordinary Hall effect lead to the conclusion that there exists a small number of itinerant electrons in ${\text{RuO}}_{2}$ layers that exhibit colossal magnetoresistance.