Within this study, we show that a broad range of reduced phases La₂NiO₃F_2−Δ can be derived from Ruddlesden–Popper-type La₂NiO₃F₂ using a reductive topochemical defluorination method based on reactions between the oxyfluoride and sodium hydride. The selective extraction of fluoride results in strong structural changes, and the nuclear and magnetic structures of the obtained phases have been determined. Due to the high anion content in La₂NiO₃F₂, the formation of Ni⁺-containing compounds has been observed under reduction. For the first time, this has led to the formation of the highest reduced end member with a T′-type structure with an approximate composition of La₂NiO₃F in the n = 1 Ruddlesden–Popper-type series containing only Ni⁺ as the B-cation. This compound can be described as stacking of alternating (La/O₂/La) fluorite-type layers with La_n–1(NiO₂)_n infinite layer structural blocks. The underlying reaction mechanism has been investigated by means of X-ray and neutron diffraction, elemental analysis, and magnetic measurements. Furthermore, to gain a deeper understanding of structural distortions, density functional theory-based calculations were performed, providing information about structural rearrangements upon defluorination and magnetic interactions. It is highlighted that the presence of even small amounts of d⁹-configured Ni⁺ cations leads to strong structural changes in La₂NiO₃F_1.93, introducing long-range antiferromagnetic ordering between the adjacent perovskite building blocks by increasing the Ni–X–X–Ni super-superexchange interactions as compared to stoichiometric La₂NiO₃F₂.

中文翻译：

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La ₂ NiO ₃ F _2的拓扑化学还原：第一个基于镍的Ruddlesden–Popper n = 1 T'型结构及其还原对磁有序的影响

在这项研究中，我们表明，使用还原性拓扑化学脱氟方法，基于氧氟化物与钠之间的反应，可以从Ruddlesden-Popper型La ₂ NiO ₃ F ₂衍生出多种还原相La ₂ NiO ₃ F2 _-Δ。氢化物。氟化物的选择性萃取导致强烈的结构变化，并且已经确定了所获得相的核和磁结构。由于La ₂ NiO ₃ F _2中的高阴离子含量，Ni ⁺的形成在还原下已观察到含-化合物。首次，这导致形成的最高减少端件的与T'-型结构的拉近似组合物₂的NiO ₃中的F Ñ = 1 Ruddlesden-波普型仅含有镍系列⁺作为B-阳离子。这种化合物可以描述为交替的（La / O ₂ / La）萤石型层与La _{n – 1}（NiO ₂）_n的堆叠无限层结构块。已通过X射线和中子衍射，元素分析和磁测量研究了潜在的反应机理。此外，为了更深入地了解结构畸变，进行了基于密度泛函理论的计算，提供了有关脱氟和磁相互作用时结构重排的信息。需要强调的是，即使少量的d ⁹构型的Ni ⁺阳离子的存在也会导致La ₂ NiO ₃ F _1.93发生强烈的结构变化。，与化学计量的La ₂ NiO ₃ F ₂相比，通过增加Ni–X–X–Ni超超交换相互作用，在相邻的钙钛矿构件之间引入了远距离反铁磁有序。