Quadruple Perovskite Manganites*

We present the discovery and refinement by neutron powder diffraction of a new magnetic phase in the Na_1−xCa_xMn₇O₁₂ quadruple perovskite phase diagram, which is the incommensurate analogue of the well known pseudo-CE phase of the simple perovskite manganites. We demonstrate that incommensurate magnetic order arises in quadruple perovskites due to the exchange interactions between A and B sites. Furthermore, by constructing a simple mean field Heisenberg exchange model that generically describes both simple and quadruple perovskite systems, we show that this new magnetic phase unifies a picture of the interplay between charge, magnetic, and orbital ordering across a wide range of compounds.