Anisotropic magnetic structures of the MnRMnSbO6 high-pressure doubly ordered perovskites (R=La, Pr, and Nd)

A new type of doubly ordered perovskite (also reported as double double perovskite, DDPv) structure combining columnar and rock-salt orders of the cations at the $A$ and $B$ sites, respectively, was recently found at high pressure for $\mathrm{Mn}R\mathrm{MnSb}{\mathrm{O}}_{6}$ ($R=\mathrm{La}\text{--}\mathrm{Sm}$). Here we report further magnetic structures of these compounds. $\mathrm{M}{\mathrm{n}}^{2+}$ spins align into antiparallel ferromagnetic sublattices along the $x$ axis for $\mathrm{MnLaMnSb}{\mathrm{O}}_{6}$, while the magnetic anisotropy of $\mathrm{P}{\mathrm{r}}^{3+}$ magnetic moments induces their preferential order along the $z$ direction for $\mathrm{MnPrMnSb}{\mathrm{O}}_{6}$. The magnetic structure of $\mathrm{MnNdMnSb}{\mathrm{O}}_{6}$ was reported to show a spin-reorientation transition of $\mathrm{M}{\mathrm{n}}^{2+}$ spins from the $z$ axis towards the $x$ axis driven by the ordering of $\mathrm{N}{\mathrm{d}}^{3+}$ magnetic moments. The crystal-field parameters for $\mathrm{P}{\mathrm{r}}^{3+}$ and $\mathrm{N}{\mathrm{d}}^{3+}$ at the $4e\phantom{\rule{0.16em}{0ex}}{C}_{2}$ site of their DDPv structure have been semiempirically estimated and used to derive their energy levels and associated wave functions. The results demonstrate that the spin-reorientation transition in $\mathrm{MnNdMnSb}{\mathrm{O}}_{6}$ arises as a consequence of the crystal-field-induced magnetic anisotropy of $\mathrm{N}{\mathrm{d}}^{3+}$.