Evidence of unconvensional density wave in low dimensional organic compounds

低维有机化合物中非常规密度波的证据

基本信息

批准号：
15540349
负责人：
KAWAMATA Shuichi
金额：
$ 2.3万
依托单位：
Osaka Prefecture University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2004
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-15540349/
关键词：
Electron spin resonance Organic compounds BEDT-TSF molecule LabVIEW Measurement automation Magnetic field control Metal insulator transition Superconductivity 温度制御

项目摘要

In a electron spin resonance (ESR) measurement by using a cavity, it is important that the temperature is well controlled to be constant in order that the frequency should be stable. In the ESR measurement system, a lock-in amplifier to detect output, a constant voltage generator for the precise magnetic field control and the temperature controller are connected to a computer through IEEE-488 interface. The program is made to conduct the measurement automatically by using LabVIEW software.The organic compound λ-(BEDT-TSF)_2Fe_<1-x>Ga_xCl_4(x=0,0.4,1.0) is the typical example of so called n-d system. There is the strong correlation between the Π electrons at the BEDT-TSF molecules and the d electrons at Fe ions. For x=0, the material shows the paramagnetic metal above 9K and it becomes the antiferromagnetic insulator below 9 K. As the Ga concentration x increases, the metal insulator transition temperature decreases. For x>5.0, the superconducting phase appears. For the material with x= … More 0, the anomaly in the π electrons are reported by the dielectric response, the specific heat, the proton NMR and the X-ray diffraction measurements at around 70 K in addition to the metal insulator transition at 9 K.The g-value and the line width along H//a^*, H//b^* and H//c are measured in the temperature range from 1.5 to 300 K, The magnetic field direction dependencies are measured at several temperatures between 20 and 300 K. In the ESR measurements for the crystal with x=0, only one resonance signals observed in the temperature range from 7 to 300 K. The magnetic field direction dependencies at 120 K do not show the symmetry of the two-dimensional conducting plane. Therefore, the response from the π electrons is combined with that from the d electrons of Fe ions. The shift of the g-value and the enhancement of the line width are observed below 70 K. It is a strong evidence of the strong π-d coupling that the ESR anomaly occurs accompanied by the anomaly in the π electrons.For the crystal with x=0.4, similar anomaly in the ESR signal is observed. This suggests the dielectric anomaly also in the compounds except for x=0. In the case of the crystal with x=1.0, both of the temperature dependencies and magnetic field direction dependencies show that the ESR signal originates from the π electrons as expected. Less

在通过使用腔度的电子自旋共振（ESR）测量中，重要的是，温度得到很好的控制才能保持恒定，以便频率应保持稳定。在ESR测量系统中，一个用于检测输出的锁定放大器，用于精确磁场控制和温度控制器的恒定电压发生器通过IEEE-488接口连接到计算机。该程序是通过使用LabView软件自动进行测量的。在BedT-TSF分子处的π电子与Fe离子的D电子之间存在很强的相关性。对于X = 0，材料显示了9K以上的顺磁金属，它变成了9K以下的抗磁管绝缘子。随着GA浓度X的增加，金属绝缘子过渡温度降低。对于x> 5.0，出现超导阶段。对于具有X =…更多0的材料，π电子中的异常是通过比热的特定热量，质子NMR和X射线衍射测量在70 K处的测量值，除了9 K时的金属绝缘子过渡外，G值和线宽度沿H // a^*，H // B^*和H // c insies contrencies in 1.5 tose nive in 1.5 tone in nive in 1.5在20至300 K之间的几个温度下。在ESR测量值中，X = 0的晶体，在温度范围为7至300 K中仅观察到一个共振信号。120 K处的磁场方向依赖关系并未显示二维导电平面的对称性。因此，将π电子的响应与Fe离子的D电子的响应结合在一起。在70 K以下观察到G值的移位和线宽的增强。这是强烈的π-D偶联的有力证据，即ESR异常发生在π电子中的异常发生。对于具有X = 0.4的晶体，ESR信号中的异常异常。这表明除x = 0外，化合物中的温和异常。在x = 1.0的晶体的情况下，温度依赖性和磁场方向依赖性都表明，ESR信号源自预期的π电子。较少的