Vortex pinning and dynamical behavior in Nb–InAs composite thin films compared with Nb
摘要
The vortex pinning and vortex dynamics of Nb–InAs composite thin films containing vertically aligned InAs nanorods were systematically investigated using combined analyses of pinning force scaling and activation energy. The field dependence of the activation energy Ueff exhibits two distinct regimes, characterized by relatively weak field dependence at low fields and significantly stronger field dependence at higher fields. The corresponding exponent α increases from values close to unity at low fields to substantially larger values at higher fields, suggesting a crossover in vortex dynamics. Dew–Hughes scaling analysis further indicates that a single-component description is insufficient to reproduce the full field dependence of the normalized pinning force density, particularly in the high-field region where the decrease in pinning force becomes more gradual. This behavior is more consistently described using a two-component model with peak positions near b ≈ 0.35 and b ≈ 0.6, implying the coexistence of different pinning characteristics. The overall results suggest that the pinning force scaling mainly reflects static pinning characteristics, while Ueff provides complementary information on vortex dynamics in Nb–InAs composite thin films.