Intrinsic Triple Order in A-site Columnar-Ordered Quadruple Perovskites: Proof of Concept

There is an emerging topic in the science of perovskite materials: A-site columnar-ordered A₂ A'A''B₄ O₁₂ quadruple perovskites, which have an intrinsic triple order at the A sites. However, in many examples reported so far, A' and A'' cations are the same, and the intrinsic triple order is hidden. Here, we investigate structural properties of Dy₂ CuMnMn₄ O₁₂ (1) and Ho₂ MnGaMn₄ O₁₂ (2) by neutron and X-ray powder diffraction and prove the triple order at the A sites. The cation distributions determined are [Ho₂ ]_A [Mn]_A' [Ga_0.66 Mn_0.34 ]_A'' [Mn_3.66 Ga_0.34 ]_B O₁₂ and [Dy₂ ]_A [Cu_0.73 Mn_0.27 ]_A' [Mn_0.80 Dy_0.20 ]_A'' [Mn_1.89 Cu_0.11 ]_B1 [Mn₂ ]_B2 O₁₂ . There are clear signatures of Jahn-Teller distortions in 1 and 2, and the orbital pattern is combined with an original type of charge ordering in 1. Columnar-ordered quadruple perovskites represent a new playground to study complex interactions between different electronic degrees of freedom. No long-range magnetic order was found in 2 by neutron diffraction, and its magnetic properties in low fields are dominated by an impurity with negative magnetization or magnetization reversal. On the other hand, 1 shows three magnetic transitions at 21, 125, and 160 K.