In this work we analyze the influence of random point defects introduced by 3 MeV proton irradiation on the critical current density (J c ) and vortex dynamics of a Ba(Fe 0.925 Co 0.075 ) 2 As 2 single crystal. The results show that at low temperatures (T ) the irradiation produces an enhancement of J c of up to 2.6 times. However the J c (T ) retention at different magnetic fields (H ) in the elastic regime, estimated by the n exponent in J c vs (1 − (T /T c ) 2 ) n , is poorer after the irradiations due to the thermal softening of the pinning by the random point defects. We found that the elastic-to-plastic crossover and melting lines are only affected by the reduction of the superconducting critical temperature (T c ); they are exactly the same after rescaling the phase diagram by T /T c . The pinning mechanisms in the single crystals can be associated with a mixed pinning landscape that produces a modulation in S(H , T ) as a consequence of a fishtail or second peak in the magnetization.
We report the influence of random point defects introduced by 3 MeV proton irradiation (doses of 0.5×10 16 , 1×10 16 , 2×10 16 and 6×10 16 cm −2 ) on the vortex dynamics of co-evaporated 1.3 μm thick, GdBa 2 Cu 3 O 7−δ coated conductors. Our results indicate that the inclusion of additional random point defects reduces the low field and enhances the in-field critical current densities J c . The main in-field J c enhancement takes place below 40 K, which is in agreement with the expectations for pinning by random point defects. In addition, our data show a slight though clear increase in flux creep rates as a function of irradiation fluence. Maley analysis indicates that this increment can be associated with a reduction in the exponent μ characterizing the glassy behavior.
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