Insulator-Metal Transitions in the BaCoS_2-xSex and BaCo_0.9Ni_0.1S_2-xSex Systems
Abstract
The compound BaCoS2 is a quasi-two-dimensional antiferromagnetic insulator with a Néel temperature above 300 K. The structure consists of CoS sheets separated by BaS rock-salt layers. Single crystal x-ray diffraction has shown that Se preferentially substitutes for S in the BaS layers causing an increase in the separation between the CoS and BaS layers. Electrical and magnetic measurements indicate that the compounds BaCoS_2-xSex exhibit a transition from antiferromagnetic insulator to paramagnetic metal with increasing x for 0 <= x <= 1. Near x = 0.3 there is evidence for anomalous magnetic behavior above 150 K. Sulfur deficient BaCo_0.9Ni_0.1S_2-x has been shown to exhibit an unusual insulator to metal (IM) transition with decreasing temperature.(Martinson, Schweitzer, and Baenziger, Phys. Rev. Lett. 71), 125 (1993) Nominally stoichiometric BaCo_0.9Ni_0.1S_2-xSex displays the same IM transition as seen in the non-substituted, sulfur deficient materials, but with a much higher transition temperature. Implications for the mechanism of the IM transition in these materials will be discussed.
- Publication:
-
APS March Meeting Abstracts
- Pub Date:
- March 1997
- Bibcode:
- 1997APS..MAR.C1909M