Composition-driven crystal structure transformation and magnetic properties of electrodeposited Co–W alloy nanowires

The cobalt (Co)–tungsten (W) alloys exhibit unique combinations of mechanical and magnetic properties, biocompatibility, resistance against corrosion, wear, and high-temperature, which makes them desirable materials for various practical applications. A nanoporous template with incorporated Co–W alloy nanowires is a soft magnetic composite, whose dielectric and magnetic properties can be tuned through the host material, pore distribution and size, Co–W composition and crystal structure, and geometry of the nanowires. Here, we report the composition-dependent structural and magnetic properties of Co–W alloy nanowires embedded in alumina templates by electrodeposition. The addition of W transforms cobalt from the crystalline hexagonal-close-packed (hcp) Co to a mixed nanocrystalline/amorphous-like Co(W) solid solution with ferromagnetic behavior and composition similar to that of the weakly magnetic Co₃W compound. The combination of the approach to magnetic saturation, anisotropy field distribution method, micromagnetic simulations, and first-order reversal curve diagram identification method elucidates the structure-driven magnetization reversal processes in both individual nanowires and magnetostatically coupled array as a whole.