  We explore the relative strengths of spin orbit coupling and crystal field
splitting in the Ir5+ compounds Ba2-xSrxYIrO6. In the case of strong spin orbit
coupling and regular Ir5+ octahedra, one expects a nonmagnetic J = 0 state; in
the case of distorted octahedra where crystal field effects dominate, the t2g
manifold splits into a magnetic ground state. We report the results of
continuously transitioning from the cubic Ba2YIrO6 double perovskite with ideal
octahedra to the monoclinic Sr2YIrO6 double perovskite with distorted
octahedra. We see no emergence of an enhanced Ir5+ magnetic moment in the
series on increasing the structural distortions, as would have been the case
for significant crystal field splitting. The near-constant magnetic moment
observed through the Ba2-xSrxYIrO6 series reinforces the notion that spin-orbit
coupling is the dominant force in determining the magnetism of iridium-oxygen
octahedra in perovskite-like structures
