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

点击翻译按钮获取中文摘要

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. ***