MgB2 superconductor samples, co-doped with 0.02 wt of Al2O3 and 0.02 wt SiC, have been examined by M-H loop measurements and calculation of the critical current density based on the Bean model. Normalized volume pinning force, f= F/Fmax, as a function of the reduced magnetic field, h =H/Hmax has been obtained at each temperature. Hughochi flux pinning model, which was included the normal point pinning, the normal surface pinning, and the pinning based on spatial variation in the Ginzburg–Landau parameter, was used to study the flux pinning mechanisms. It was found that theΔκeffect and the normal point pinning mechanisms play the main role in the flux pinning at the magnetic field lower than Hmax and the contribution of the Δκ mechanism increases with the increasing temperature, while the contribution of normal point pinning mechanism decreases. At magnetic field larger than Hmax, the only mechanism that acts as the flux pinning was the normal surface pinning mechanism.

Keywords