Effects of impurities and temperature on the thermal hysteresis of Ohmic resistance in Tl-doped blue bronze.

Abstract

The thermal hysteresis of Ohmic resistance was investigated in the pure and K- and W-substituted Tl blue bronze samples in the temperature range of 30-180 K. The results show that the hysteresis begins at the charge-density-wave (CDW) phase transition temperature T-p, and exists in a wide temperature range. The hysteresis quantified by Delta R(s)/R(m), the normalized resistance difference between the two saturation curves, increases with decreasing temperature. The behavior of the transit curve is characterized by its average d(2)[R/R(T-rev)]/dT(2), which increases with a decrease of the reversing temperature T-rev. For the effects of substitutional doping, d(2)[R/R(T-rev)]/dT(2) of the transit curve increases with impurity monotonically while the hysteresis quantity Delta R(s)/R(m) is enhanced by low-level weak pinning doping and reduced by heavily weak pinning doping or a strong pinning impurity. The present results support that the hysteresis quantity is controlled by pinning and CDW domain size, while d(2)[R/R(T-rev)]/dT(2) of the transit curve is determined only by pinning.