Coexistence of the δl and δTc flux pinning mechanism in nano-Si doped MgB2

Abstract

The flux pinning mechanisms of nano-Si-doped MgB2 are reported in this work. The field<br><br>dependence of the critical current density, Jc(B), was analyzed within the collective pinning<br><br>model. We found that the mechanisms for both δl pinning, i.e., pinning associated with<br><br>charge-carrier mean free path fluctuations, and δTc pinning, which is associated with spatial<br><br>fluctuations of the transition temperature, coexist in the nano-Si-doped MgB2 samples, while<br><br>Hc2 increases greatly with increasing nano-Si doping level. However, their contributions are<br><br>strongly temperature dependent. The δl pinning is dominant at low temperatures, decreases<br><br>with increasing temperature, and is suppressed completely at temperatures close to the critical<br><br>temperature, Tc. However, the δTc pinning mechanism shows opposite trends.