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

技术摘要：最近的观测为层状三元硫化化合物BaCo1-xNixS2-y中不寻常的金属-绝缘体（MI）转变提供了证据。初步的解释表明，随着温度的降低，从二维反铁磁半导体转变为金属。我们将使用电阻率、霍尔效应、直流和交流磁化率以及红外吸收技术来详细研究这种MI转变。所得结果将与用Cu取代Ni的三元化合物进行比较。用x射线粉末衍射对材料进行结构分析。使用的理论模型哈密顿量将类似于先前用于La2CuO的理论模型哈密顿量，并为BaCo1-xMxS2-y系统提供适当的参数，并在相干势近似内处理无序。非技术摘要：最近在含有Ba， Co, Ni（或cu）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，从半导体转变为金属。这种不寻常的转变将使用实验和理论技术进行更详细的研究。与这种转变相关的热双稳定性和正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. ***