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

One of the drawbacks of using high-coercivity materials for magnetic data storage is the need for large write head fields for data writing. In attempts to solve this problem, we have fabricated an array of CoPt/Ni composite nanowires using anodized aluminum oxide (AAO) templates, electrochemical deposition, and an annealing treatment. The array consists of vertically aligned, ~25-nm diameter, composite nanowires with ~80-nm-long, magnetically soft Ni at the base and ~20-nm-long, magnetically hard, L1₀ phase CoPt at the top. To see the influence of the composite structure on the magnetic properties, separate samples with Ni and CoPt nanowires of the same height were prepared and annealed using identical conditions. M-H loops along the nanowire axis show that the Ni nanowires exhibit relatively soft magnetic coercivity of 242 Oe, while the CoPt nanowires show a very high coercivity of 10.97 kOe. The composite CoPt/Ni nanowires exhibit an intermediate coercivity of 1.96 kOe. The results show a reduction in coercivity versus the CoPt nanowires, potentially leading to easier data writing