Resistance anomaly in quasi-one-dimensional sulfide BaNbS3+δ

Single-phase specimens of hexagonal BaNbS3+delta (2.93 less than or equal to 3 + delta less than or equal to 3.06) have been successfully prepared by the sulfurization method using CS2. The lattice constants, a and c, are less sensitive to the value of delta in the region of -0.07 less than or equal to delta less than or equal to 0.06. BaNbS2.93 indicates a semiconductor-to-semiconductor gradual transition around 100 K. On the other hand, BaNbS3+delta (2.96 less than or equal to 3 + delta less than or equal to 3.06) shows hump-shaped anomalous behaviors in the resistivity. Although the anomalies in the electrical resistivity have been observed, all the samples have indicated no anomaly in their magnetic susceptibility. The magnetic susceptibilities are nearly temperature independent with extremely small Curie-like behavior at low temperatures. BaNbS2.98 does not undergo a structural phase transition and there is no change in symmetry down to 80 K, above which the hump-shaped anomaly is clearly found. The relationship in the resistance anomaly between BaNbS3+delta and BaVS3 seems to be significant and to have an important role in clarifying the mechanism of these anomalies. (C) 1999 Academic Press.