Cu-induced tailoring of microstructure and magnetization reversal in FeCoNi nanowires

In this study, the influence of Cu addition on the morphology, elemental composition, structure, and magnetic properties of FeCoNi nanowires is investigated. FeCoNiCu nanowires were electrodeposited at various cathodic potentials in polycarbonate membranes with a pore diameter of 80 nm and a channel length of 6 μm. Electrochemical analysis indicates easier reduction in Cu-containing systems, yet associated with charge-transfer limitations. The samples exhibit homogeneous elemental distributions, except at the nanowire ends in samples deposited at lower potentials, where Cu-rich regions are observed. Increasing the cathodic potential leads to an increase in Ni content, accompanied by a simultaneous decrease in the content of the other elements. Cu incorporation results in grain refinement and increased defect density, but does not affect the crystallographic texture; the polycrystalline fcc phase retains preferred growth directions along [111] and [220] at lower and higher potentials, respectively. The Cu-containing samples exhibit significantly higher coercivity and squareness, along with lower saturation magnetization, compared to Cu-free samples. These changes are attributed to increased defect density and dilution of the magnetic matrix due to the addition of diamagnetic Cu, respectively. However, the evolution of these parameters within the Cu-containing series is governed primarily by dipolar interactions. The weak angular dependence of coercivity and Cu-dependent switching field distribution indicate a complex magnetization reversal process arising from competing interactions, with dipolar coupling playing a dominant role in FeCoNiCu nanowires. These systems predominantly exhibit a single-domain structure, with a slight vortex-like domain formation at the nanowire ends.