Experimental Study of Layered Ternary Sulfide Alloys with Unusual Metal-Insulator Transition

9318385 Schweitzer技术摘要：最近的观察为层状三元硫化物BaCo1-xNixS2-y中不寻常的金属-绝缘体(MI)转变提供了证据。初步解释认为，这种转变是从二维反铁磁半导体到温度降低的金属的转变。将使用电阻率、霍尔效应、直流和交流磁化率以及红外吸收技术详细研究这种MI转变。结果将与用铜取代镍的三元化合物进行比较。用X射线粉末衍射仪对材料进行了结构分析。对于BaCo1-xMxS2-y系统和在相干势近似下处理无序的情况下，所用的理论模型哈密顿量将类似于以前对La2CuO所采用的模型。非技术摘要：最近在含有Ba、Co、Ni(ORCuO)和S原子的材料中发现了一种不寻常的转变。随着温度的降低，从半导体到金属的转变。这一不寻常的转变将用实验和理论技术进行更详细的研究。与这一转变相关的热双稳和正的电阻率温度系数表明，该材料可用于各种电光应用。***

9318385 Schweitzer Technical abstract: Recent observations have provided evidence for an unusual metal-insulator (MI) transition in the layered ternary sulfide compound BaCo1-xNixS2-y. A preliminary interpretation proposes that the transition is from a two-dimensional antiferromagnetic semiconductor to a metal with decreasing temperature. This MI transition will be investigated in detail using resistivity, Hall effect, dc and ac susceptibility, and infrared absorption techniques. The results will be compared with the ternary compound in which Ni is replaced by Cu. The materials will be structurally analyzed by x-ray powder diffraction. Theoretical model Hamiltonians used will be similar to those employed previously for La2CuO with appropriate parameters for the BaCo1-xMxS2-y system and with disorder treated within the coherent potential approximation. Non-technical abstract: An unusual transition has been discovered recently in material containing Ba, Co, Ni (orCu), and S atoms. The transition is from a semiconductor to a metal as the temperature is decreased. This unusual transition will be investigated in greater detail using experimental and theoretical techniques. The thermal bistability and positive temperature coefficient of resistivity associated with this transition suggests that the material could be useful for a variety of electro-optic applications. ***