Interaction between the Ferromagnetic Dots and Vortices: Numerical Calculation and Experimental Results

Abstract

Enhancing the pinning force in high-Tc superconductors can be achieved by externally introduced periodic magnetic dots. We numerically calculate the interaction between ferromagnetic dots and vortices in high-Tc superconductors. The London equation is used to generate two-dimensional vortex lattice. In the matching condition, we calculate the attraction force between magnetic dots and vortices. It is found that in an ideal condition, the pinning force of the magnetic dot reaches 2.5×10−11 N that is more than one order magnitude stronger than the intrinsic pinning force in YBa2Cu3O7 thin films. In the experimental side, we use a novel nano-technique to deposit periodic submicron Ni dots on YBa2Cu3O7 thin films. The current versus voltage characteristics of an YBa2Cu3O7 thin film strip with uniform Ni dots are measured at various temperatures and magnetic fields. They are compared with the current versus voltage characteristics of a bare YBa2Cu3O7 thin film strip without magnetic dots. It is found the critical current value of the strip with Ni dots reduces with a much slower pace as the magnetic field strength increases in comparison with the value of the bare sample.