Tunable pinning in superconducting films with magnetic micro-loops
  We study the flux pinning properties of superconductor/magnetic micro-rings lattice hybrid structures. The used open triangular micromagnets represent an eight-fold degree of freedom system, with six polarized and two flux-closure possible states. By conveniently choosing the magnetic state of the underlying rings it is possible to induce different pinning potentials. We show that the magnetic vortex state with minimum stray field produces a weaker pinning in comparison with the polarized states. 
A. V. Silhanek, W. Gillijns, V. V. Moshchalkov, V. Metlushko, B. Ilic