Scaling Behavior in Aluminum Doped MgB2 Superconductor

Magnetization measurements have been performed on Mg1-xAlxB2 (0 <= x <= 0.1) at various temperatures below T-c and in fields up to 9 T. The reversible magnetization has been used to calculate the thermodynamic critical field (H-c) which is then used to obtain a new universal behavior for both the critical current density (J(c)) and the pinning force (P-f). This approach is based on vortex core energy (similar to H-c(2)) and clearly exhibits the deviation from single vortex pinning with increasing temperature and higher concentration of Al-doping.