  We present a neutron powder diffraction study of the monoclinic double
perovskite systems Nd2NaB'O6 (B' = Ru, Os), with magnetic atoms occupying both
the A and B' sites. Our measurements reveal coupled spin ordering between the
Nd and B' atoms with magnetic transition temperatures of 14 K for Nd2NaRuO6 and
16 K for Nd2NaOsO6. There is a Type I antiferromagnetic structure associated
with the Ru and Os sublattices, with the ferromagnetic planes stacked along the
c-axis and [110] direction respectively, while the Nd sublattices exhibit
complex, canted antiferromagnetism with different spin arrangements in each
system.
