Using Wannier functions to represent the density functional results we calculate the hybridization corrections to the orbital momentum operator in the Os 5d shell of the Mott insulators Ba2NaOsO6 and Ba2YOsO6. The g-factors are obtained by evaluating the spin and orbital momentum operators in the atomic ground states of the Os ion.
While the hybridization corrections play a minor role in the d(3) ion of Ba2YOsO6 with a dominant spin moment, they are instrumental for the observation of the nonzero g-factor of the d(1) ions of Ba2NaOsO6. In addition, we analyze the exchange interactions in Ba2YOsO6 and find them to be consistent with the reported magnetic structure.