New Stacking Variations of the CE-type Structure in the Metal-Ordered Manganite YBaMn2O6

For the paramagnetic insulating phase in the metal-ordered manganite YBaMn2O6, the so-called CE-type of charge/orbital ordered state was observed within the monoclinic ab-plane, which is most commonly observed for the ordinary half doped manganites. However, TEM revealed a 4-fold periodicity along the c-axis, suggesting a new stacking pattern, where planes of the CE-type are built up according to the sequence [aabb...]. Interestingly, when th system enters into the antiferromagnetic state, this stacking pattern changes into [aaaa...] or [abab], suggesting close interplay between spins and orbitals. These features are discusses in terms of inherent structural alternation, i.e., the Y/Ba order along the c-axis.