Nanoimprint-Lithography Patterned Epitaxial Fe Nanowire Arrays with Misaligned Magnetocrystalline and Shape Anisotropies

We fabricated large area (>1 × 1 cm 2 ), epitaxial Fe nanowire arrays on MgO(001) substrates by nanoimprint lithography with a direct metallization of epitaxial materials through a metallic mask, which avoided the disadvantageous metal-etching process in conventional methods. The magnetization reversals, as revealed by magneto-optic Kerr effect, showed competing effects between Fe cubic magnetocrystalline anisotropy and lithographically induced uniaxial shape anisotropy. Unlike the weakly induced uniaxial anisotropy observed in continuous films, both the magnitude and direction of the uniaxial shape anisotropy can be easily modulated in the nanowires. Complex magnetization reversal processes including two-step and threestep loops were observed when magnetizing the samples along different Fe cubic easy axes, respectively. These modified magnetization reversal processes were explained by the nucleation and propagation of the domain walls along the non-superimposed easy axes of the competing magnetocrystalline and shape anisotropies.