We have investigated the temperature dependence and applied magnetic-field dependences of critical current densities Jc(H, T) and the irreversibility lines Hirr(T) obtained from the magnetization measurements in HgBa2(Ca1-xSrx)2Cu3O8+δ and Hg0.5Tl0.5Ba2(Ca1-xSrx)2Cu3O8+δ. Jc(H, T) and Hirr(T) of Hg0.5Tl0.5Ba2(Ca1-xSrx)2Cu3O8+δ are found to be higher than those of HgBa2(Ca1-xSrx)2Cu3O8+δ, indicating that the Tl substitution at Hg sites provides additional flux pinning. Jc(H, T) has been analyzed using the flux-creep model. Jc(H, T) in magnetic fields above 1 T is well described by the flux-creep model. However, the thermal activation energy estimated by fitting the data to the flux-creep model shows different behaviors above and below about 65 K for both HgBa2(Ca1-xSrx)2Cu3O8+δ and Hg0.5Tl0.5Ba2(Ca1- xSrx)2Cu3O8+δ. Also, in Hirr(T) a crossover from a power-law temperature dependence above 65 K to a more rapid dependence below 65 K is observed in both samples. Although the origin of such a crossover in Hirr(T) and Jc(H, T) is not clear, the two phenomena are considered to be closely related.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Energy Engineering and Power Technology
- Electrical and Electronic Engineering