Li4NiOsO6和Li3Ni2OsO6型岩盐的合成，晶体结构和3d-5d协同磁性。,Inorganic Chemistry

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Li4NiOsO6和Li3Ni2OsO6型岩盐的合成，晶体结构和3d-5d协同磁性。
Inorganic Chemistry ( IF 4.3 ) Pub Date : 2020-05-09 , DOI: 10.1021/acs.inorgchem.9b03249
Phuong-Hieu T Nguyen ₁ , JoAnna Milam-Guerrero ₂ , Gia T Tran ₁ , Charles J Bloed ₁ , Abbey J Neer ₂ , Anh Nguyen ₃ , Thomas Gredig ₃ , Ashfia Huq ₄ , Saul H Lapidus ₅ , Brent C Melot ₂ , Shahab Derakhshan ₁

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成功合成了两种标称化学成分为Li ₄ NiOsO ₆和Li ₃ Ni ₂ OsO _6的新型过渡金属氧化物。两种化合物都以单斜C 2 / m空间群的有序岩盐结构类型结晶。使用同步加速器X射线和飞行时间中子粉末衍射数据确定晶体结构。在这两个阶段中，在Li ₄ NiOsO ₆和Li ₃ Ni ₂ OsO _6中，Ni的氧化态分别为+6和+5时，存在Ni ²⁺离子。镍²⁺假设的全序相中的离子在ab晶面中形成蜂窝排列，并且这些六边形以by离子为中心。磁性层沿c轴被八面体隔开，八面体以Li ⁺（或Li ⁺ / Ni ²⁺，取决于化学成分）。晶体结构的改进表明，阳离子位置存在一定程度的混合占据。两个相的温度相关磁化率数据显示，在镍的3d电子和的5d电子之间具有主要反铁磁（AFM）相互作用的亚铁磁跃迁。在转变温度以下，等温磁化回路是所施加磁场的函数，证实了磁性转变中的亚铁磁性。然而，与温度相关的热容数据在任何一个相中均未显示任何异常，这表明没有长程磁序。Os ⁵⁺和Os ⁶⁺都缺乏远程顺序低至10 K的低温中子衍射数据也证实了基团化合物。两种样品在不同频率下随温度变化的AC磁化率数据表明Li ₄ NiOsO ₆表现出自旋玻璃状的行为，而Li ₃的转变温度Ni ₂ OsO ₆几乎与频率无关。

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Synthesis, Crystal Structure, and Cooperative 3d-5d Magnetism in Rock Salt Type Li4NiOsO6 and Li3Ni2OsO6.

Two new transition metal oxides with the nominal chemical compositions of Li₄NiOsO₆ and Li₃Ni₂OsO₆ were successfully synthesized. Both compounds crystallize in an ordered rock salt structure type in the monoclinic C2/m space group. The crystal structures were determined using both synchrotron X-ray and time-of-flight neutron, powder diffraction data. In both phases, Ni²⁺ ions are present while oxidation states of osmium are +6 and +5 in Li₄NiOsO₆ and Li₃Ni₂OsO₆, respectively. Ni²⁺ ions in the hypothetical fully ordered phase form a honeycomb arrangement in the ab crystallographic plane and these hexagons are centered by osmium ions. The magnetic layers are separated along the c axis by the octahedra, which are centered by Li⁺ (or Li⁺/Ni²⁺, depending on the chemical compositions). Crystal structure refinements reveal that there is some degree of mixed occupancy in cationic positions. Temperature dependent magnetic susceptibility data for both phases show ferrimagnetic transitions with predominant antiferromagnetic (AFM) interactions among 3d electrons of nickel and 5d electrons of osmium. Iso-thermal magnetization loops as a function of the applied magnetic field below the transition temperatures confirm the ferrimagnetic nature in magnetic transitions. Temperature dependent heat capacity data, however, did not exhibit any anomaly in either phase, indicating the absence of long-range magnetic ordering. The lack of long-range order for both Os⁵⁺ and Os⁶⁺-based compounds was also confirmed by low temperature neutron diffraction data down to 10 K. Temperature dependent AC magnetic susceptibility data in various frequencies for both samples indicate that Li₄NiOsO₆ exhibits spin-glass-like behavior, while the transition temperature for Li₃Ni₂OsO₆ is nearly frequency independent.

更新日期：2020-05-09

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