Pinning properties and vortex dynamics in thin superconducting films with ferromagnetic and antiferromagnetic arrays of magnetic dots

Abstract

We report on the simulations of the pinning properties and vortex dynamics in thin superconducting film with three different periodic arrays of magnetic dots: (1) all magnetic dots have the same magnetization orientation (ferromagnetic pinning array); (2) magnetic dots with up and down magnetization orientation are arranged alternatively, to form an antiferromagnetic two-dimensional array; and (3) the same as the previous array, but each dot is replaced by a $2\ifmmode\times\else\texttimes\fi{}2$ magnetic dot subarray. All dots in the subarray have the same magnetization orientation. We calculated the critical depinning force and magnetization as a function of the applied magnetic field for these three arrays. Due to the field polarity-dependent flux pinning effect of the magnetic dots, asymmetric pinning behavior in the first array can be switched to the symmetric one in the latter two arrays while keeping the pronounced matching effects. We also calculated the current-voltage characteristics at both commensurate and incommensurate fields. We found that at the first matching field, the transition from the pinned phase to a vortex motion phase is continuous for the ferromagnetic configuration but discontinuous for the two antiferromagnetic configurations. This can be explained by different vortex dynamical trajectories. Our results indicate that pinning properties and vortex dynamics in thin superconducting films can be manipulated by tuning the configuration of the magnetic dot array.