Structure and Electronic Properties of the Quasi-One-Dimensional Ba₂Co_1-xZn_xS₃ Series

This work focuses on the structure and physical properties of the solid solution Ba₂Co_1-xZn_xS₃ (0 ≤ x ≤ 1), a family of quasi-one-dimensional sulfides with end members Ba₂CoS₃ and Ba₂ZnS₃. The structure of selected compounds with increasing Zn²⁺ content has been analyzed using neutron diffraction, transmission electron microscopy, and extended X-ray absorption fine structure, and the physical properties have been analyzed via magnetic susceptibility and resistivity measurements. The progressive substitution of the nonmagnetic Zn²⁺ cation for Co²⁺ rapidly destroys the antiferromagnetic transition present at 46 K in the quasi-one-dimensional Ba₂CoS₃, leading to paramagnetic behavior down to the lowest investigated temperature (5 K) for compounds with x > 0.25. For compounds with x ≥ 0.4, a pure Curie-Weiss regime is recovered around 300 K, yielding effective moments consistent with the g factor of the tetrahedrally coordinated Co²⁺ previously determined for Ba₂CoS₃. The substitution of Zn²⁺ for Co²⁺ also removes the metallic-like behavior of Ba₂CoS₃, causing an increase in the value of the resistivity with all the Ba₂Co_1-xZn_xS₃ compounds showing semiconducting behavior. The negative magnetoresistance of Ba₂CoS₃ is improved by the substitution of Zn²⁺ for Co²⁺, with values of -6% for Ba₂Co_0.75Zn_0.25S₃, -9% for Ba₂Co_0.5Zn_0.5S₃, and -8% for Ba₂Co_0.25Zn_0.75S₃. However, there does not seem to be a correlation between the values of resistivity and magnetoresistance and the content of Zn²⁺, leading to the hypothesis that transport properties may be linked more closely to extrinsic properties.