Perovskite Metal Formate Framework of [NH2-CH+-NH2]Mn(HCOO)3]: Phase Transition, Magnetic, Dielectric, and Phonon Properties
Perovskite Metal Formate Framework of [NH2-CH+-NH2]Mn(HCOO)3]: Phase Transition, Magnetic, Dielectric, and Phonon Properties
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DOI：
10.1021/ic500479e
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发表时间：
2014-05-19
影响因子：
4.6
通讯作者：
Drozd, Marek
中科院分区：
文献类型：
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作者：
Maczka, Miroslaw;Ciupa, Aneta;Drozd, Marek
我们报告了 [NH2-CH+-NH2][Mn(HCOO)(3)] (FMDMn) 的合成、晶体结构以及热、介电、声子和磁性能。 [(Mn(HCOO)(3)(-)]的阴离子骨架被位于骨架空腔中的甲脒(FMD+)阳离子平衡。这些阳离子与骨架形成广泛的N-H中心点中心点中心点O氢键。二价锰离子具有八面体几何形状，并通过甲酸盐以反反配位模式桥接。我们发现FMDMn在周围发生结构相变。 335 K。根据 X 射线衍射，该化合物在 355 K 时显示出 R (3) 对称性，在 295 和 110 K 时显示出 C2/c 对称性。FMD+ 阳离子在高温相中动态无序，这种无序导致与 NH2 基团振动相对应的拉曼和红外波段带宽非常大。温度依赖性研究表明，FMDMn 中的相变与有序化有关。然而，详细分析表明，这些阳离子在低至约 200 K 时仍表现出一些重新取向运动。FMD+ 阳离子的排序与阴离子骨架的显着变形有关。根据磁性数据，FMDMn 是一种弱铁磁体，其临界温度 T-c = 8.0 K。
We report the synthesis, crystal structure, and thermal, dielectric, phonon, and magnetic properties of [NH2-CH+-NH2][Mn(HCOO)(3)] (FMDMn). The anionic framework of [(Mn(HCOO)(3)(-)] is counterbalanced by formamidinium (FMD+) cations located in the cavities of the framework. These cations form extensive N-H center dot center dot center dot O hydrogen bonding with the framework. The divalent manganese ions have octahedral geometry and are bridged by the formate in an anti anti mode of coordination. We have found that FMDMn undergoes a structural phase transition around 335 K. According to the X-ray diffraction, the compound shows R (3) over barc symmetry at 355 K and C2/c symmetry at 295 and 110 K. The FMD+ cations are dynamically disordered in the high-temperature phase, and the disorder leads to very large bandwidths of Raman and IR bands corresponding to vibrations of the NH2 groups. Temperature-dependent studies show that the phase transition in FMDMn is associated with ordering of the FMD+ cations. Detailed analysis shows, however, that these cations still exhibit some reorientational motions down to about 200 K. The ordering of the FMD+ cations is associated with significant distortion of the anionic framework On the basis of the magnetic data, FMDMn is a weak ferromagnet with the critical temperature T-c = 8.0 K.