Quasistatic magnetic processes in magnetic nanostructures
Ferromagnetic nanostructures find potential applications in nonvolatile magnetic memory, data storage, recording heads, magnetic resonance imaging, biomedicine and biotechnology, spin torque nano oscillators (STNOs) and magnonic crystals. We have studied some of the quasistatic magnetic processes in a complex shaped Co nanodot array (rectangular shaped nanodots with ledges) arranged in rectangular symmetry. Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), Magnetic Force Microscopy (MFM) and Micromagnetic Simulations have been employed to study the quasistatic magnetic properties of this sample. The MFM images show quasi-single domain behavior of the nanomagnets in the remanence. Micromagnetic simulations show a vortex state in remanence after saturation in the direction perpendicular to the ledge and a nearly single domain state in remanence after saturation in the direction of the ledge. Interestingly, when the ledge of the nanomagnets is not considered, a simple “S” state is observed in remanence after saturation in the direction perpendicular to the ledge and a vortex state in remanence after saturation in the direction of the ledge. The remanent magnetic state is found to be very sensitive to the shape of the nanodot and the orientation of the applied magnetic field due to the shape anisotropy.
Keywords: nanomagnetism, atomic force microscopy, energy dispersive X-ray, hysteresis, micromagnetic simulations, magnetic force microscopy