New BETS conductors with magnetic anions (BETS equivalent to bis(ethylenedithio)tetraselenafulvalene)
New BETS conductors with magnetic anions (BETS equivalent to bis(ethylenedithio)tetraselenafulvalene)
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DOI：
10.1021/ja9523350
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发表时间：
1996-01-17
影响因子：
15
通讯作者：
Cassoux, P
中科院分区：
文献类型：
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作者：
Kobayashi, H;Tomita, H;Cassoux, P
报道了(BETS)₂MX₄分子导体（BETS = 双(乙烯二硫代)四硒富瓦烯；M = Mn²⁺、Fe³⁺、Co²⁺、Ni²⁺、Cu²⁺；X = Cl、Br、CN）的制备、晶体结构以及电学和磁学性质。低至2 K的电阻率测量揭示了在K-(BETS)₂FeCl₄和κ-(BETS)₄(CoCl₄)(C₂H₃Cl₃)盐中BETS的π传导电子和阴离子的局域磁矩共存。另一种FeCl₄相，λ-(BETS)₂FeCl₄，在约8 K处发生急剧的金属 - 绝缘体（MI）转变。在相同温度下，FeCl₄⁻阴离子协同发生磁转变。在λ-(BETS)₂(FeCl₄)₀.₅(GaCl₄)₀.₅中，在4.6 K处观察到超导转变，其中一半的阴离子位点被磁性离子占据。由含NiCl₄²⁻和MnCl₄²⁻阴离子的1,1,2 - 三氯乙烷溶液制备的晶体在低至约100 K时表现出半金属行为。(BETS)₄(Cu₂Cl₆)盐在低至4.2 K时仍为金属态。电子自旋共振（ESR）研究表明，κ - 和λ-(BETS)₂FeCl₄中的Fe³⁺离子处于高自旋态。κ - 和λ-(BETS)₂FeCl₄的自旋磁化率随温度的变化表明Fe³⁺离子之间存在反铁磁相互作用。对κ - 和λ-(BETS)₂FeCl₄在298 K和10 K进行了晶体结构分析。观察到λ-(BETS)₂FeCl₄中BETS…FeCl₄的接触更紧密，这与该化合物较大的外斯温度一致。
The preparation, crystal structures, and electric and magnetic properties of (BETS)(2)MX(4) molecular conductors (BETS = bis(ethylenedithio)tetraselenafulvalene; M = Mn2+, Fe3+, Co2+, Ni2+, Cu2+; X = Cl, Br, CN) are reported. Resistivity measurements down to 2 K reveal the coexistence of the BETS pi conduction electrons and the localized magnetic moments of the anions in the K-(BETS)(2)FeCl4 and kappa-(BETS)(4)(CoCl4)(C2H3Cl3) salts. Another FeCl4 phase, lambda-(BETS)(2)FeCl4, undergoes a sharp metal-insulator (MI)) transition around 8 K. At the same temperature, a magnetic transition of the FeCl4-anions takes place cooperatively. A superconducting transition is observed at 4.6 K in lambda-(BETS)(2)(FeCl4)(0.5)(GaCl4)(0.5), where half of the anion sites are occupied by magnetic ions. The crystals prepared from 1,1,2-trichloroethane solutions with the NiCl42- and MnCl42- anions exhibit the behavior of a semimetal down to approximate to 100 K. The (BETS)(4)(Cu2Cl6) salt remains metallic down to 4.2 K. ESR studies show that the Fe3+ ions in kappa- and lambda-(BETS)(2)FeCl4 are in a high-spin state. The temperature dependencies of the spin susceptibilities of kappa- and lambda-(BETS)(2)FeCl4 indicate antiferromagnetic interactions between the Fe3+ ions. The crystal structure analyses of kappa- and lambda-(BETS)(2)FeCl4 have been carried out at 298 and 10 K. Closer BETS ... FeCl4 contacts in lambda-(BETS)(2)FeCl4 are observed, which is consistent with the larger Weiss temperature of this compound.