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

在本研究中，硫系尖晶石CuRh_2S_4中压致超导绝缘体相变的机制被理解为Yb金属中的能带简并猝灭和CuIR_2S_4中发现的一种新的电荷有序的双重作用。室温附近从金属到半金属输运性质的变化是由于能带简并猝灭。变种猫猫科动物。T*以下的变化是由于收费顺序造成的。利用压力感生的超导绝缘体转变的新函数，我们可以构造一种新的有源器件。在新材料的开发方面，我们已经成功地合成了CuCrZrS4，CuCr2Te4，CeMg2(Cu_&lt；L-x&gt；，Nix)_9多晶。我们发现CuCrZrS_4在58K经历了铁磁转变。然而，令人惊讶的是，在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造成的。我们测定了CuCr2Te4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T_c=324K时发生铁磁相变。从380K到650K的居里-魏斯型磁化率随温度的变化关系，我们得到了4.14μ〓/铬离子的有效磁矩和+357K的魏斯温度。低温磁化强度符合布洛赫定律和T^&lt；3/2&gt；和T^&lt；5/2&gt；对于CeMg2(Cu1-x；1-x&gt；Nix)9，x=0和0.2的化合物分别在2.5K和1.7K表现出显著的比热反常。比热异常的起源是一种反铁磁性相变。我们还从比热中的肖特基类反常确定了这些化合物中4f电子的晶场喷射能级方案。作为我们研究的新领域，我们测量了笼形原子的固态性质。

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.