Coupled Nd andB′spin ordering in the double perovskites Nd2NaB′O6(B′=Ru, Os)

Abstract

We present a neutron powder-diffraction study of the monoclinic double perovskite systems Nd${}_{2}$Na${B}^{\ensuremath{'}}$O${}_{6}$ (${B}^{\ensuremath{'}}=\text{Ru}$, Os), with magnetic atoms occupying both the $A$ and ${B}^{\ensuremath{'}}$ sites of the ${A}_{2}B{B}^{\ensuremath{'}}{\text{O}}_{6}$ structure. Our measurements reveal coupled spin ordering between the Nd and ${B}^{\ensuremath{'}}$ atoms with magnetic transition temperatures of 14.3(1) K for Nd${}_{2}$NaRuO${}_{6}$ and 16.2(2) K for Nd${}_{2}$NaOsO${}_{6}$. 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.