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Mechanism and novel functions of pressure-induced superconductor-insulator transition in chalcogenide spinels

硫族尖晶石压力诱导超导-绝缘体转变的机制和新功能

基本信息

批准号：
17340113
负责人：
SUZUKI Takashi
金额：
$ 10.48万
依托单位：
Hiroshima University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2005
资助国家：
日本
起止时间：
2005 至 2007
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-17340113/
关键词：
Chalcogeniele sninel Pressure-induced sunerconductor insulator transiti Development of novel functions New materials Caged atoms 比熱強磁性

项目摘要

In this study, he mechanism of the pressure-induced superconductor insulator transition in chalcogenide spinel CuRh_2S_4 has been understood as the dual effects of a band degeneracy quenching bind in Yb-metal and a novel charge ordering found in CuIr_2S_4. The change in transport property around room temperature from metallic to semimetallic one is due to the band degeneracy Quenching. The tranpcat ptherty . change below T* is due to the charge ordering. Using a novel function of the pressure-induced superconductor insulator transition, we can construct a new active device. We are now preparing to apply a patentAs for a development of new materials, we have succeeded in synthesizing poly crystals of CuCrZrS_4, CuCr_2Te_4, CeMg2(Cu_<l-x>,Ni_x)_9.We have found that CuCrZrS_4 undergoes a ferromagnetic transition at 58K. However, there in no specific heat anomaly around 58K, surprisingly. This phenomenon can be due to a successive spin freezing. We have determined the crystal structure of CuCr_2Te_4, which has a cubic spinel structure with a = 11.134A. We also found for the first time that this compound undergoes a ferromagnetic transition at Tc = 324K. From the Curie-Weiss type temperature dependence of magnetic susceptibility between 380 and 650K, we obtained the effective magnetic moment of 4.14μ〓/Cr-ion and the Weiss temperature of +357K The low temperature magnetization shows Bloch's T^<3/2> and T^<5/2> law, which suggests a spin excitation. As for CeMg2(Cu_<1-x>Ni_x)_9, both compounds with x = 0 and 0.2 show remarkable specific heat anomalies at 2.5K and 1.7K, respectively. The origin for the specific heat anomalies is an antiferromagnetic transition. We also determined the crystal field spritting level scheme of 4f electron in these compound from the Schottky-type anomalies in the specific heat. As a new landscape of our study, we measured the solid state properties of a caged atom.

在本研究中，硫系尖晶石CuRh_2S_4中压力诱导超导体绝缘体转变的机制被理解为Yb-metal中的能带简并淬火结合和CuIr_2S_4中发现的新电荷有序的双重作用。室温下从金属到半金属输运性能的变化是由于能带简并淬火。运输理论。T*以下的变化是由于收费顺序。利用压力感应超导体绝缘体跃迁的新函数，我们可以构建一种新的有源器件。我们已经成功地合成了CuCrZrS_4， CuCr_2Te_4, CeMg2(Cu_<l-x>,Ni_x)_9的多晶，目前正在准备申请新材料的开发专利。我们发现CuCrZrS_4在58K时发生了铁磁跃迁。然而，令人惊讶的是，58K附近没有比热异常。这种现象可能是由于连续的自旋冻结。我们测定了CuCr_2Te_4的晶体结构，它具有立方尖晶石结构，a = 11.134A。我们还首次发现该化合物在Tc = 324K时发生铁磁跃迁。根据磁化率在380 ~ 650K之间的居里-魏斯型温度依赖，我们得到了有效磁矩为4.14μ〓/Cr-ion， Weiss温度为+357K，低温磁化符合Bloch的T^<3/2>和T^<5/2>定律，表明存在自旋激发。对于CeMg2(Cu_<1-x>Ni_x)_9，当x = 0和0.2时，分别在2.5K和1.7K表现出明显的比热异常。比热异常的来源是一个反铁磁跃迁。我们还从比热的肖特基型异常中确定了这些化合物中4f电子的晶体场喷射能级方案。作为我们研究的一个新领域，我们测量了笼化原子的固态性质。