Coexistence of the delta l and delta T-c flux pinning mechanisms in nano-Si-doped MgB2

摘要

The flux pinning mechanisms of nano-Si-doped MgB2 are reported in this work. The field dependence of the critical current density, J(c)(B), was analyzed within the collective pinning model. We found that the mechanisms for both delta l pinning, i.e., pinning associated with charge-carrier mean free path fluctuations, and delta T-c pinning, which is associated with spatial fluctuations of the transition temperature, coexist in the nano-Si-doped MgB2 samples, while H-c2 increases greatly with increasing nano-Si doping level. However, their contributions are strongly temperature dependent. The delta l pinning is dominant at low temperatures, decreases with increasing temperature, and is suppressed completely at temperatures close to the critical temperature, T-c. However, the delta T-c pinning mechanism shows opposite trends.