Quantitative analysis of the guidance of vortices in superconducting films with magnetic dots

Abstract

The guidance of vortices in superconducting Nb films with periodic arrangements of magnetic Ni dots is studied via simultaneous four-probe measurements in standard and Hall configuration. Ni dots are fabricated via e-beam lithography and lift-off technology. Arrays with periodicity down to 400 nm and dot size of 200 nm are obtained. Subsequently, the arrays are covered with a thin superconducting Nb layer. Simultaneous Hall and standard resistive measurements of the flux dynamic in Nb bridges with and without magnetic dots demonstrate and quantify the guidance of flux via the magnetic dots. Guidance of vortices is only possible in a limited current regime; guidance improves with decreasing temperature. Within the identified current regime most of the vortices (>40% for zero field) and in the optimum case all of the vortices are guided by the magnetic dots.