Thermally activated flux flow in pristine and proton-irradiated Ca_8.5La_1.5(Pt₃As₈)(Fe₂As₂)₅ single crystals

We investigate the influence of the proton irradiation on the thermally activation flux flow (TAFF) on the mixed state in Ca_8.5La_1.5(Pt₃As₈)(Fe₂As₂) single crystals using the magnetoresistivity in magnetic fields up to 13T for B//c-axis and B//ab-plane. We found that the effect of thermally activated flux flow is well described by the nonlinear temperature-dependent activation energy in both pristine and proton irradiated sample. The magnetic field dependence of the activation energy follows a power law of U₀(B)∼B^−α where the exponent α is changed from crossover field of around 3T, indicating that the strength of vortex pinning is weaker as a result of proton irradiation. We suggest that the pristine and proton irradiated sample dominate 2D vortex phase in the TAFF region.