Domain wall displacement in Py square ring for single nanometric   magnetic bead detection
  A new approach based on the domain wall displacement in confined ferromagnetic nanostructures for attracting and sensing a single nanometric magnetic particles is presented. We modeled and experimentally demonstrated the viability of the approach using an anisotropic magnetoresistance device made by a micron-size square ring of Permalloy designed for application in magnetic storage. This detection concept can be suitable to biomolecular recognition, and in particular to single molecule detection. 
P. Vavassori, V. Metlushko, M. Gobbi, M. Donolato, M. Cantoni, R.   Bertacco