engleski

High pressure transport study of Co1/3NbS2

Co1/3NbS2 belongs to the family of the transition-metal intercalated transition metal dichalcogenides. Co occupies octahedral positions between the trigonal prismatic layers of the host compound 2H NbS2, resulting in a 3 × 3 superlattice. Two electrons per Co atom are transferred to the initially half– filled 2 z d − band of the host NbS2 which thereby broadens and becomes 5/6 filled. The remaining seven electrons on the Co ion are localized and form magnetic moments with a quenched orbital contribution (3/2 spin-only moment). These moments order antiferromagnetically (known as the hexagonal ordering of the first kind) at the Néel temperature of 26 K. This transition is driven by two competing interactions: the RKKY and the superexchange via neighboring S ions. A way to vary the relative strength of these interactions is by applying pressure. We have measured the electrical resistivity and thermopower at room pressure from 1.6 to 300 K and under pressures (up to 1.8 GPa in the temperature range of 1.6 to 300 K). In addition, thermal conductivity was measured at room pressure from 2 to 300 K. Resistivity is metallic– like with a change in slope at the Néel temperature. This is interpreted as diminution of the spin– disorder upon entrance into the antiferromagnetic state. Transition temperature is shifted to lower values with increasing hydrostatic pressure accompanied by development of a resistivity minimum. Thermopower on the other hand exhibits non– metallic behavior above 100 K and a small maximum at 10 K which diminishes and appears at lower temperatures upon applying pressure. Thermal conductivity is also unusual and bears very little change at the Néel temperature.

transition metal dichalcogenides; Co1/3NbS2; transport properties; high pressure

The paper was presented by Igor Smiljanić.