Self-organized structures of orbital-ordered domains inNd1−xSr1+xMnO4

Abstract

Self-organizing domain structures of charge-orbital-ordered (COO) and ferro-orbital-ordered (FOO) phases were observed for tetragonal layered manganites ${\text{Nd}}_{1\ensuremath{-}x}{\text{Sr}}_{1+x}{\text{MnO}}_{4}$ ($x=0.8$ and 0.82) by low-temperature transmission electron microscopy. We revealed a marked temperature variation of coexisting COO domains with equivalent structural distortions and orbital ordering patterns at $x=0.8$. The observed competition of coexisting FOO domains at $x=0.82$ also clearly reflects the self-organizing nature of ${e}_{g}$ electrons. Furthermore, a checkered structure, in which COO domains were reproduced at the intersections of FOO domains, was found in the transition from the COO phase to the FOO phase at $x=0.8$. The observations suggest that strain energy affects the self-organizing behavior in the orbital ordering.