Graduate School of Engineering, Kyoto University, Kyoto 615-8510 (Japan); The Hakubi Center for Advanced Research, Kyoto University, Kyoto 606-8501 (Japan).
Angew Chem Int Ed Engl. 2015 Jan 7;54(2):516-21. doi: 10.1002/anie.201408483. Epub 2014 Nov 21.
The synthesis, structure, and magnetic properties of a polar and magnetic oxynitride MnTaO2N are reported. High-pressure synthesis at 6 GPa and 1400 °C allows for the stabilization of a high-density structure containing middle-to-late transition metals. Synchrotron X-ray and neutron diffraction studies revealed that MnTaO2N adopts the LiNbO3-type structure, with a random distribution of O(2-) and N(3-) anions. MnTaO2N with an "orbital-inactive" Mn(2+) ion (d(5); S=5/2) exhibits a nontrivial helical spin order at 25 K with a propagation vector of [0,0,δ] (δ≈0.3), which is different from the conventional G-type order observed in other orbital-inactive perovskite oxides and LiNbO3-type oxides. This result suggests the presence of strong frustration because of the heavily tilted MnO4N2 octahedral network combined with the mixed O(2-)/N(3-) species that results in a distribution of (super)-superexchange interactions.
报道了一种极性和磁性的氧氮化物 MnTaO2N 的合成、结构和磁性。在 6 GPa 和 1400°C 的高压下合成，可以稳定含有中晚期过渡金属的高密度结构。同步加速器 X 射线和中子衍射研究表明，MnTaO2N 采用 LiNbO3 型结构，其中 O(2-)和 N(3-)阴离子随机分布。具有“轨道非活性”Mn(2+)离子(d(5); S=5/2)的 MnTaO2N 在 25 K 时表现出非平凡的螺旋自旋有序，传播矢量为 [0,0,δ]（δ≈0.3），与其他轨道非活性钙钛矿氧化物和 LiNbO3 型氧化物中观察到的常规 G 型有序不同。这一结果表明，由于 MnO4N2 八面体网络的严重倾斜以及 O(2-)/N(3-)混合物种的存在，导致（超）超交换相互作用的分布，存在强烈的受挫。
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