Structure and electronic properties of the quasi-one-dimensional Ba$_2$Co$_{1–x}$Zn$_x$S$_3$ Series
Résumé
This work focuses on the structure and physical properties of the solid solution Ba$_2$Co$_{1–x}$Zn$_x$S$_3$ (0 ≤ x ≤ 1), a family of quasi-one-dimensional sulfides with end members Ba$_2$CoS$_3$ and Ba$_2$ZnS$_3$. The structure of selected compounds with increasing Zn$^{2+}$ 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$^{2+}$ cation for Co$^{2+}$ rapidly destroys the antiferromagnetic transition present at 46 K in the quasi-one-dimensional Ba$_2$CoS$_3$, 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$^{2+}$ previously determined for Ba$_2$CoS$_3$. The substitution of Zn$^{2+}$ for Co$^{2+}$ also removes the metallic-like behavior of Ba$_2$CoS$_3$, causing an increase in the value of the resistivity with all the Ba2Co1–xZnxS3 compounds showing semiconducting behavior. The negative magnetoresistance of Ba$_2$CoS$_3$ is improved by the substitution of Zn$^{2+}$ for Co$^{2+}$, with values of −6% for Ba$_2$Co$_{0.75}$Zn$_{0.25}$S$_3$, −9% for Ba$_2$Co$_{0.5Z}$n$_{0.5}$S$_3$, and −8% for Ba$_2$Co$_{0.25}$Zn$_{0.75}$S$_3$. However, there does not seem to be a correlation between the values of resistivity and magnetoresistance and the content of Zn$^{2+}$, leading to the hypothesis that transport properties may be linked more closely to extrinsic properties.
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