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

本文将硫系尖晶石CuRh_2S_4的压致超导体转变机理理解为Yb金属的能带简并猝灭和CuIr_2S_4中新的电荷有序的双重作用。室温附近的输运性质由金属态转变为半金属态是由于能带简并猝灭。那只迷幻猫低于T* 的变化是由于电荷排序。利用压力诱导超导体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CuCrZrS_4、CuCr_2Te_4、CeMg_2（Cu_<l-x>，Ni_x）_9等多晶材料。然而，令人惊讶的是，在58 K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，α = 11.134。我们还首次发现该化合物在Tc = 324 K发生铁磁转变。从380 ~ 650 K的居里-韦斯型磁化率温度关系，得到了有效磁矩为4.14μ π ι/Cr ~（3+），韦斯温度为+357 K。低温磁化强度符合布洛赫T^&lt;3/2&gt;和T^&lt;5/2&gt;定律，表明是自旋激发。对于CeMg_2（Cu_<1-x>Ni_x）_9，x = 0和x = 0.2的化合物分别在2.5K和1.7K出现了明显的比热反常。比热异常的起源是反铁磁转变。从比热的Schottky型反常确定了这些化合物中4f电子的晶场分裂能级图。作为我们研究的一个新领域，我们测量了笼中原子的固态性质。

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.