The investigation of the substitution of calcium for strontium in the composite spin chain structure of the oxide Sr_11/8(Mn_5/8Co_3/8)O_3+δ has been performed combining powder/single crystal X-ray diffraction and 3D electron diffraction. A large family of composite commensurate/incommensurate spin chain structures A_1+y[(Mn_5/8Co_3/8)_1–z□_z]O₃, built up of face sharing MnO₆/CoO₆ octahedra and a CoO₆ trigonal prism and containing cationic vacancies (□) on the prismatic sites, has been synthesized, varying the alkaline earth ion content on the A site according to the nominal composition Sr_11–nCa_nMn₅Co₃O₂₄. It is shown that the structural nature of the chains and content of cationic vacancies can be directly designed from the Ca/Sr ratio, based on the larger oxidation power of strontium compared to calcium during synthesis in air. In this way, the cationic vacancy content z can be significantly decreased from 1/33 to 0.002 by increasing the Ca content from n = 0 to n = 6.8. Correlatively, the proportion of dimeric units (1 octahedron/1 trigonal prism) with respect to trimeric units (2 octahedra/1 trigonal prism) increases continuously from 0 to 1/3 as the Ca content increases from n = 0 to n = 6.8. It is also shown that the influence of the proportion of these dimeric/trimeric units on the magnetism of these oxides is remarkable, suggesting that, besides the size effect of calcium, it plays a role in the appearance of long-range ordering in this system.

中文翻译：

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由二聚体和三聚体多面体单元构成的复合自旋链结构：氧化物 A1+y[(Mn1–xCox)1–z□z]O3 (A = Ca, Sr; x = 3/8)

结合粉末/单晶X射线衍射和3D研究，研究了氧化物Sr _11/8 (Mn _5/8 Co _3/8 )O _3+δ复合自旋链结构中钙对锶的取代作用。电子衍射。一大类复合自旋链结构 A _{1+ y} [(Mn _5/8 Co _3/8 ) _{1– z} □ _z ]O ₃，由共享面的 MnO ₆ /CoO ₆八面体和 CoO _{6组成已经合成了三棱柱并在棱柱位上含有阳离子空位（□），根据标称成分 Sr 11– n} Ca _n Mn ₅ Co ₃ O ₂₄改变 A 位上的碱土离子含量。结果表明，基于在空气中合成过程中锶与钙相比具有更大的氧化能力，可以根据 Ca/Sr 比直接设计链的结构性质和阳离子空位的含量。这样，通过将 Ca 含量从n = 0 增加到n ，阳离子空位含量z可以从 1/33 显着降低到 0.002= 6.8。相关地，随着 Ca 含量从n = 0 增加到n = 6.8 ，二聚体单元（1 个八面体/1 个三棱柱）相对于三聚体单元（2 个八面体/1 个三棱柱）的比例从 0 连续增加到 1/3 。还表明，这些二聚体/三聚体单元的比例对这些氧化物的磁性影响显着，这表明除了钙的尺寸效应外，它还在该系统中的长程有序出现中起作用.