THE PHASE DIAGRAM OF NEW ORGANIC SUPERCONDUCTOR BETS SALTS WITH A MIXED HALIDE GALLIUM ANION

新型有机超导体与混合卤化镓阴离子的盐相图

基本信息

批准号：
08454217
负责人：
KOBAYASHI Akiko
金额：
$ 3.58万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1996
资助国家：
日本
起止时间：
1996 至 1997
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-08454217/
关键词：
molecular superconductor phase diagram BETS organic superconductor

项目摘要

In 1996, crystal structures, electrical resistivities and magnetic susceptibilities of a series of organic superconductors with tetrahedral mixed halide gallium anions, lambda-BETS2GaXzY4-z (X,Y=F,Cl, Br ; 0<z<4) having triclinic unit cells and fourfold quasi-stacking arrangement of BETS (=bis (ethylene-dithio) tetraselenafulvalene) molecules were examined. The resistivity behavior dependedon the size of anion. The superconducting behavior could be examined systematically by exchanging the halogen atoms (X,Y) and the z-value. The magnetic susceptibilities were studied on lambda-BETS_2GaCl_3F and lambda-BETS_2GaBr_zCl_<4-z> (0<z<1.5). Although the resistivity behaviors of lambda-BETS_2GaX_zY_<4-z> resemble closely those of so-called 10K-class kappa-type BEDT-TTF superconductors, the insulating ground state near the superconducting state is non-magnetic. Theoretically this non-magnetic phase is pointed out that it has the possibility of exsisting on the borderline of spin-gap phase and antiferromagnetic phase. This year this non-magnetic phase was examined precisely by ^1H-NMR.^1H-NMR did not exhibit the abrupt increase of 2nd moment, which was observed in kappa-(ET)_2[CuN(CN)_2]Cl. In lambda-(BETS)_2GaCl_<2.5>Br_<1.5> the divergence of 1/T_1 which is characteristicin forming the magnetic orderness was not observed within the temperature range from 25K to 2K.So this phase is considered not as antiferromagnetic phase but as non-magnetic phase. lambda'-BETS3GaBr4 has a modified lambda-type structure and it shows narrow-gap semiconducting behavior down to 50K.lambda'-BETS3GaBr4 transforms to the insulating phase below 50 K.The decrease of magnetic susceptibilities with the anisotropies parallel to H and perpendicular to H was observed below 60 K.This phase transition seems to be antiferromagnetic. Such a high temperature antiferromagnetic phase transition of organic molecules is very rare and very interesting, compared with high-temperature inorganic superconductors.

1996年，一系列具有三斜晶胞的四面体混合卤化镓阴离子有机超导体，lambda-BETS2GaXzY4-z (X,Y=F,Cl, Br ; 0<z<4)的晶体结构、电阻率和磁化率BETS（=双（乙二硫）四硒富瓦烯）分子的四重准堆积排列为检查了。电阻率行为取决于阴离子的大小。通过交换卤素原子 (X,Y) 和 z 值可以系统地检查超导行为。研究了 lambda-BETS_2GaCl_3F 和 lambda-BETS_2GaBr_zCl_<4-z> (0<z<1.5) 的磁化率。尽管 lambda-BETS_2GaX_zY_<4-z> 的电阻率行为与所谓的 10K 级 kappa 型 BEDT-TTF 超导体非常相似，但超导状态附近的绝缘基态是非磁性的。理论上指出这种非磁性相有可能存在于自旋能隙相和反铁磁性相的边界上。今年，通过^1H-NMR对这种非磁性相进行了精确检查。^1H-NMR没有表现出在kappa-(ET)_2[CuN(CN)_2]Cl中观察到的二阶矩的突然增加。在 lambda-(BETS)_2GaCl_<2.5>Br_<1.5> 中，在 25K 至 2K 的温度范围内没有观察到形成磁有序性的特征 1/T_1 的发散。因此，该相不被认为是反铁磁相，而是被认为是非磁性相。 lambda'-BETS3GaBr4 具有改进的 lambda 型结构，在低至 50K 时表现出窄带隙半导体行为。lambda'-BETS3GaBr4 在 50 K 以下转变为绝缘相。磁化率随着各向异性平行于 H 和垂直于 H 的降低而降低。在低于 60 K 时观察到 H。这种相变似乎是反铁磁性的。与高温无机超导体相比，有机分子的如此高温反铁磁相变非常罕见且非常有趣。