Structure and Electronic Properties of the Quasi-One-Dimensional BaCoZnS Series.

This work focuses on the structure and physical properties of the solid solution BaCoZnS (0 ≤ x ≤ 1), a family of quasi-one-dimensional sulfides with end members BaCoS and BaZnS. The structure of selected compounds with increasing Zn 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 Zn cation for Co rapidly destroys the antiferromagnetic transition present at 46 K in the quasi-one-dimensional BaCoS, 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 Co previously determined for BaCoS. The substitution of Zn for Co also removes the metallic-like behavior of BaCoS, causing an increase in the value of the resistivity with all the BaCoZnS compounds showing semiconducting behavior. The negative magnetoresistance of BaCoS is improved by the substitution of Zn for Co, with values of -6% for BaCoZnS, -9% for BaCoZnS, and -8% for BaCoZnS. However, there does not seem to be a correlation between the values of resistivity and magnetoresistance and the content of Zn, leading to the hypothesis that transport properties may be linked more closely to extrinsic properties.