The evolution of magnetic behavior in FeCoNi nanowires with different geometry

FeCoNi nanowires (NWs) with different diameters (40–120 nm) and lengths (1.5–6 µm) were electrodeposited in the polycarbonate membranes. Magnetic measurements confirmed anisotropy along the NW axis. Changes in the nanowire geometry resulted in increased coercivity and squareness for smaller diameters. Studies of the magnetization reversal mechanism showed a non-monotonic coercivity variation as a function of angle, pointing out the initial vortex domain wall propagation that transformed into a transverse or coherent rotation at angles closer to the hard direction. FORC analysis confirmed that the nanowire diameter is the main factor determining magnetostatic interaction between nanowires and indicated a non-interacting system in the case of a small diameter NW matrix. Magnetic imaging of the sample using Lorentz microscopy did not reveal domain walls, which together with FORC results, implies a single-domain structure of nanowires. Therefore, the obtained nanowires meet the criteria required for 3D racetrack memory applications.