Alternative charge-order polymorph for half-doped manganites inTbBaMn2O6

The half-doped manganite perovskite ${\mathrm{TbBaMn}}_2{\mathrm{O}}_6\left({\mathrm{Tb}}_{0.5}{\mathrm{Ba}}_{0.5}{\mathrm{MnO}}_3\right)$ has been prepared by low-temperature oxygen intercalation into ${\mathrm{TbBaMn}}_2{\mathrm{O}}_5.$ Neutron powder diffraction shows that at 300 K, ${\mathrm{TbBaMn}}_2{\mathrm{O}}_6$ has a triclinic distorted perovskite superstructure exhibiting long-range order of the ${\mathrm{Tb}}^{3+}$ and ${\mathrm{Ba}}^{2+}$ cations, displacements of the intercalated oxygens, ${\mathrm{Mn}}^{3+}$ and ${\mathrm{Mn}}^{4+}$ charge states, and ${\mathrm{Mn}}^{3+}$ orbital states. The “rocksalt” charge order is different from the “striped” arrangement found in many other half-doped manganite perovskites such as $\left({\mathrm{La}}_{0.5}{\mathrm{Ca}}_{0.5}\right){\mathrm{MnO}}_3,$ demonstrating that internal strains induced by the cations can lead to polymorphism of charge ordering in a transition-metal oxide framework.