  Effect of Co, Ru and Cu substitution at B and B' sites on the magnetic and
transport properties of LaSrCoRuO$_6$ have been investigated. All the doped
compositions crystallize in the monoclinic structure in the space group
$P2_1/n$ indicating a double perovskite structure. While the magnetization and
conductivity increase in Co and Ru doped compounds, antiferromagnetism is seen
to strengthen in the Cu doped samples. These results are explained on the basis
of a competition between linear Co-O-Ru-O-Co and perpendicular Co-O-O-Co
antiferromagnetic interactions and due to formation of Ru-O-Ru ferromagnetic
networks.
