Figure 3
Characterization of the permalloy island and magnetic bead response.
(a) A two-dimensional field intensity profile of the application of magnetic fields on the permalloy islands through our Helmholtz coils simulated using finite element method magnetics (FEMM). The red circle represents the approximate area of homogenous magnetic field where the permalloy islands are placed in the simulation. (b) Simulation results of the islands with applied external magnetic fields from the Helmholtz coils of about 80 Oe (top). Experimental comparison of these concentrated magnetic field regions through tracking ferromagnetic bead movement with the applied magnetic field (bottom). Scale bar, 10 μm. Magnetic hysteresis loop of the ferromagnetic beads and permalloy film using an alternative gradient force magnetometer (AGFM). (c) AGFM hysteresis loop of the ferromagetic beads with a coercive field of 567 Oe and (d) AGM hysteresis loop of the permalloy films with a coercive field of 14 Oe. Both magnetic hysteresis curves are normalized by the moment.
