Thermally activated flux motion in optimally electron-doped (Ca0.85La0.15)10(Pt3As8)(Fe2As2)5 and Ca10(Pt3As8)((Fe0.92Pt0.08)2As2)5 single crystals

The temperature dependence of the electric resistivity measured in various magnetic fields was analyzed by the vortex glass theory and the thermally activated flux motion (TAFM) theory. The vortex glass-to-vortex liquid (GTL) transition Tg obtained from the analysis shows a temperature dependence of B g T = B 0 1 - T / T c m . The vortex liquid region is divided into the critical region existing in a finite temperature region just above Tg and the TAFM region present in the finite temperature region above it. In the critical region, the activation energy is expressed as U e f f = k B T T c - T / ( T c - T g ) , whereas in the TAFM region, the activity energy is expressed as temperature-nonlinear U T , B = U 0 B 1 - t q . In the GTL transition, (Ca0.85La0.15)10(Pt3As8)(Fe2As2)5 maintains the 3D vortex structure without exhibiting dimension crossover of the vortex, but Ca10(Pt3As8)((Fe0.92Pt0.08)2As2)5 exhibits the dimension crossover from the 3D vortex glass to the 2D vortex liquid.