Parallel and perpendicular field dependence of JC of NbTi-Cu multilayer films

The critical current density, J_C, of NbTi-Cu multilayer films has been measured in parallel fields and in perpendicular fields at 4.2 K, as a parameter of thickness of the NbTi monolayer, d_s . The thicknesses ns are 100 nm, 200 nm, 300 nm, and 500 nm, while the thickness of the Cu monolayer is 200 nm. It is found that the cross field B* where J_C in perpendicular fields exceeds that in parallel fields clearly decreases as d_s increases. As a result of analyses of scaling parameters, the pinning force density of NbTi-Cu multilayer films in both parallel fields and perpendicular fields may be explained by the scaling law as a parameter of thickness d _s with different values of scaling parameters