Stabilization of the n = 3 Ruddlesden−Popper Phases:  Sr₄Mn_3-xFe_xO_10-δ and Sr_4-yCa_yMn₃O_10-δ

Abstract

Sr4Mn3O10, which crystallizes in space group Cmca, is not a Ruddlesden−Popper (RP) phase. The partial substitution of either Mn by Fe or Sr by Ca leads to a stable n = 3 RP phase with tetragonal symmetry (I4/mmm). The minimum amount of Fe or Ca needed to obtain a stable RP phase is x = 0.40 for Sr4Mn3-xFexO10-δ and y = 2.85 for Sr4-yCayMn3O10-δ. High-resolution transmission electron microscopy and selected area electron diffraction electron microscopy indicate that about 50% of the grains have well-ordered n = 3 structure for both series of RP phases, while the rest of the grains show significant intergrowth between the n = 2 and n = 3 structures. Sr4Mn2.6Fe0.4O10-δ and Sr1.15Ca2.85Mn3O10-δ are semiconductors and exhibit spin-glass like transitions at low temperature.