Patterned Media Based on Soft/Hard, Composite Nanowire Array of Ni/CoPt

A composite nanowire geometry consisting of soft magnetic (Ni) nanowire lower part and hard magnetic (CoPt) L1₀ nanowire upper part, has been prepared by electrodeposition into anodized aluminum oxide (AAO) nanopores with ~20-30 nm diameter, ~100 nm tall. The as-deposited nanowires within the AAO pores were then annealed at 700 degree C for 1 hour for conversion to L1₀ phase. The The microstructure and magnetic properties were characterized using scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and an alternating gradient magnetometer (AGM). When compared to Ni nanowire and CoPt nanowire coercivity, the two-step Ni/CoPt nanowires exhibit an intermediate coercivity of ~ 1.96 KOe. The decrease in coercivity may be caused by exchange interactions or the interdiffusion during annealing between the Ni and CoPt segments resulting in the formation of a ternary L1₀ alloy of Co-Pt-Ni.