Antiferromagnetic Ordering in the Single-component Molecular Conductor, [Pd(tmdt)2]
Antiferromagnetic Ordering in the Single-component Molecular Conductor, [Pd(tmdt)2]
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单组分分子导体中的反铁磁有序性，[Pd(tmdt)2]
DOI：
10.1021/acs.inorgchem.6b01166
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发表时间：
2016
影响因子：
4.6
通讯作者：
Bernard
中科院分区：
文献类型：
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作者：
Ogura Satomi;Idobata Yuki;Zhou;Biao;Kobayashi Akiko;Takagi Rina;Miyagawa Kazuya;Kanoda Kazushi;Kasai Hidetaka;Nishibori Eiji;Satoko Chikatoshi;Delley;Bernard
制备了[Pd（tmdt）2]（tmdt =三亚甲基四硫富瓦烯二硫醇盐）晶体以研究其物理性质。使用双探针法在单晶上测量[Pd（tmdt）2]的电阻率，并且显示室温电导率为100 S·cm-1。电阻率行为表明，[Pd（tmdt）2]在室温附近为半金属，当温度降低到最低温度时，[Pd（tmdt）2]变为窄禁带半导体。在20-300 K的温度下使用同步辐射在SPring-8进行的小单晶[Pd（tmdt）2]的X射线结构研究表明，在这个温度区域没有明显的结构变化。然而，在大约100 K时观察到小的异常。在2.7-301 K温度范围内测量了电子自旋共振（ESR）谱。ESR强度随着温度降低到100 K而增加，然后随着温度进一步降低到50 K而线性下降，其中观察到强度的突然下降。为了研究磁性状态，在2.5-271 K的温度范围内进行了1H核磁共振（NMR）测量，揭示了100 K以下的加宽。NMR弛豫速率在低于100 K时逐渐增加，并在约50 K处形成宽峰，随后逐渐降低至最低温度。这些结果表明，大部分样品在50 K左右发生反铁磁转变，磁有序温度分布在100 K以下的宽范围内。[Pd（tmdt）2]的这些电和磁性质与单组分分子（半）金属[Ni（tmdt）2]和[Pt（tmdt）2]的电和磁性质完全不同，后者在极低温度下保持其稳定的金属状态。在密度泛函理论水平上对[Pd（tmdt）2]的能带结构进行了计算，结果表明[Pd（tmdt）2]可能是一个具有强电子关联的反铁磁Mott绝缘体.
Crystals of [Pd(tmdt)2] (tmdt = trimethylenetetrathiafulvalenedithiolate) were prepared in order to investigate their physical properties. The electrical resistivity of [Pd(tmdt)2] was measured on single crystals using two-probe methods and showed that the room-temperature conductivity was 100 S·cm–1. The resistivity behaviors implied that [Pd(tmdt)2] was a semimetal at approximately room temperature and became narrow-gap semiconducting as the temperature was decreased to the lowest temperature. X-ray structural studies on small single crystals of [Pd(tmdt)2] at temperatures of 20–300 K performed using synchrotron radiation at SPring-8 showed no distinct structural change over this temperature region. However, small anomalies were observed at approximately 100 K. Electron spin resonance (ESR) spectra were measured over the temperature range of 2.7–301 K. The ESR intensity increased as the temperature decreased to 100 K and then decreased linearly as the temperature was further decreased to 50 K, where an abrupt decrease in the intensity was observed. To investigate the magnetic state,1H nuclear magnetic resonance (NMR) measurements were performed in the temperature range of 2.5–271 K, revealing broadening below 100 K. The NMR relaxation rate gradually increased below 100 K and formed a broad peak at approximately 50 K, followed by a gradual decrease down to the lowest temperature. These results suggest that most of the sample undergoes the antiferromagnetic transition at approximately 50 K with the magnetic ordering temperatures distributed over a wide range up to 100 K. These electric and magnetic properties of [Pd(tmdt)2] are quite different from those of the single-component molecular (semi)metals [Ni(tmdt)2] and [Pt(tmdt)2], which retain their stable metallic states down to extremely low temperatures. The experimental results and the band structure calculations at the density functional theory level showed that [Pd(tmdt)2] may be an antiferromagnetic Mott insulator with a strong electron correlation.