Origin of magnetic moments and presence of spin-orbit singlets in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi mathvariant="normal">Ba</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="normal">YIrO</mml:mi><mml:mn>6</mml:mn></mml:msub></mml:math>

While it was speculated that 5d^4systems would possess non-magnetic J=~0 ground state due to strong Spin-Orbit Coupling (SOC), all such systems have invariably shown presence of magnetic moments so far. A puzzling case is that of Ba_2IrO_6 which in spite of having a perfectly cubic structure with largely separated Ir^{5+}(d^4 ions, has consistently shown presence of weak magnetic moments. Moreover, we clearly show from Muon...