Single Crystal Growth of Sulphospinel CuIr_2S_4 which exhibits the metal-insulator transition

表现出金属-绝缘体转变的硫磷尖晶石 CuIr_2S_4 的单晶生长

• 批准号: 11640329
• 负责人: NAGATA Soichi
• 金额: $ 2.3万
• 依托单位: Muroran Institute of Technology
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1999
• 资助国家: 日本
• 起止时间: 1999 至 2000
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-11640329/
• 关键词: CuIr_2S_4; Single crystal growth; Metal-insulator transition; Sulphospinel; 5d-electron; Crystal transformation; Magnetic susceptibility; Electrical resistivity; Cu Ir_2 S_4

The normal sulphospinel CuIr_2S_4 exhibits a temperature-induced metal-insulator (M-I) transition around 226 K with structural transformation, showing hysteresis on heating and cooling With decreasing temperature, a symmetry change occurs from cubic to tetragonal symmetry and a change from the Pauli paramagnetism in metallic behavior to diamagnetism due to the atomic core orbital. A gap in the electronic density of states opens below the M-I transition temperature. It has been verified that d-electrons of Ir atom on the octahedral B-sites have a significant role for the M-I transition.Single crystals of a sulphospinel CuIr_2S_4 have been successfully grown from bismuth solution by a slow cooling method for the first time. The grown crystals have a maximum edge of about 1 mm in size and a mirror-like shining surface. Optimum growth conditions are fairly strict. The specific weight of starting materials for the crystal growth is found to be 0.30 g of CuIr_2S_4 and 10.0 g of Bi in order to obtain good quality crystals. The starting and finishing temperatures for the slow cooling step in the temperature control are 1000 and 500 ℃. The pertinent cooling rate is 〜2 ℃/h. Since the volume of bismuth itself expands in the transition from liquid phase to solid phase, a simple method of separation of the grown crystals from the liquid solution is proposed for avoiding the mechanical damages to the grown crystals. The single crystals have the normal-spinel structure of the lattice constant a =9.849 Å at room temperature. A step-like anomaly in the susceptibility of the single crystals, corresponding to the metal-insulator transition in the resistivity, occurs much sharply than in the powder specimen.

正常的硫尖晶石CuIr_2S_4在226K附近表现出温度诱导的金属绝缘体(M-I)相变，随温度的降低表现出加热和冷却的滞后，对称性从立方对称性转变为四方对称性，从金属行为的Pauli顺磁性转变为原子核轨道的抗磁性。电子态密度的能隙在M-I转变温度以下打开。证实了八面体B位Ir原子的d电子对M-I转变有重要作用，并首次从铋溶液中缓慢冷却生长出了硫尖晶石CuIr_2S_4单晶。生长的晶体最大边缘尺寸约为1 mm，表面呈镜面状。最佳生长条件是相当严格的。为了获得高质量的晶体，生长原料的比重为CuIr_2S_4 0.30g，铋10.0g。在温度控制中，慢冷步骤的开始和结束温度分别为1000和500℃。合适的冷却速度为~2℃/h。由于铋本身的体积在从液相向固相的转变过程中膨胀，因此提出了一种简单的将生长的晶体从液体中分离出来的方法，以避免对生长的晶体造成机械损伤。该单晶在室温下具有正尖晶石结构，晶格常数a=9.849Å。单晶的磁化率出现阶梯状异常，与金属-绝缘体的电阻率转变相对应，比粉末样品要剧烈得多。

项目成果

S.Nagata: "Servey of the Superconductivity in Sulfides. (in Japanese)"Metal (AGNE Publ.) No.7. 70. 542-549 (2000)

S.Nagata：“硫化物超导性的服务。（日语）”Metal（AGNE 出版）第 7 期。

S.Nagata: "Antiferromagnetic Transition in CuRh_2O_4"J. Phys. Chem. Solids. 60. 457-462 (1999)

S.Nagata：“CuRh_2O_4 中的反铁磁转变”J。

N.Matsumoto: "Resistance and Susceptibility Anomalies in IrTe_2 and CuIr_2Te_4"J.Low Temp.Phys.. 117. 1129-1133 (1999)

N.Matsumoto：“IrTe_2 和 CuIr_2Te_4 中的电阻和磁化率异常”J.Low Temp.Phys.. 117. 1129-1133 (1999)

S.Nagata: "Electronic Structure of Cu_<1-x>Ni_xRh_2S_4 and CuRh_2Se_4 : Band-structure Calculations, x-ray photoemission, and fluorescence measurements"Physical Review. B61. 4230-4237 (2000)

S.Nagata：“Cu_<1-x>Ni_xRh_2S_4 和 CuRh_2Se_4 的电子结构：能带结构计算、X 射线光电发射和荧光测量”物理评论。

G.L.W.Hart: "Electronic Structure of Cu_<1-x>Ni_xRh_2S_4 and CuRh_2Se_4 : Band-structure Calculations, X-ray Photoemission, and Fluorescence Measurements"Phys.Rev.. B61. 4230-4237 (2000)

G.L.W.Hart：“Cu_<1-x>Ni_xRh_2S_4 和 CuRh_2Se_4 的电子结构：能带结构计算、X 射线光电发射和荧光测量”Phys.Rev.. B61。