  We investigate the magnetic properties of the series Sr2Ir1-xRuxO4 with
neutron, resonant x-ray and magnetization measurements. The results indicate an
evolution and coexistence of magnetic structures via a spin flop transition
from ab-plane to c-axis collinear order as the 5d Ir4+ ions are replaced with
an increasing concentration of 4d Ru4+ ions. The magnetic structures within the
ordered regime of the phase diagram (x<0.3) are reported. Despite the changes
in magnetic structure no alteration of the Jeff=1/2 ground state is observed.
The behavior of Sr2Ir1-xRuxO4 is consistent with electronic phase separation
and diverges from a standard scenario of hole doping. The role of lattice
alterations with doping on the magnetic and insulating behavior is considered.
The results presented here provide insight into the magnetic insulating states
in strong spin-orbit coupled materials and the role perturbations play in
altering the behavior.
