Characterization of the magnetic properties of multilayer magnetostrictive iron-gallium nanowires

We investigate the magnetic properties of magnetostrictive iron-gallium (Galfenol, Fe100−xGax, 10≤x≤25 at. %) nanowires with magnetic force microscopy (MFM) and using micromagnetic modeling software (magpar). Wires with diameters of 150 nm were fabricated in alternating multilayered structures with Fe-Ga and Cu having aspect ratios of ∼2 and ∼0.5, respectively, with the goal of minimizing the relative contribution of shape anisotropy to magnetic domain alignment. Micromagnetic simulations of isolated Fe-Ga segments with these dimensions predict that (1) at remanence, two opposing vortex structures will form at the ends of a Fe-Ga segment, with a single domain wall in the middle of the segment and (2) traditional magnetic dipoles will form at the ends of the segment to align with a large (saturation) external magnetic field. MFM results are presented that support these models. At remanence, no contrast is observed in the MFM phase images. Magnetic poles become evident at the ends of the Fe-Ga segments when...