Perpendicular Magnetization: Designing Magnetism on Nanowire Arrays - Crystal and Shape Magnetic Anisotropies

Current cutting edge magnetic recording devices utilize perpendicular magnetization with heat assisted writing technologies to store information. Magnetic recording device platters are the subject of much research due to miniaturization, increasing the bit/cm2 memory capacity, new faster read/write head technologies, and fabrication simplification. This work introduces a new way to achieve a high density, perpendicularly magnetized substrates with the capacity to increase current memory density by over 104 bits/cm2 while also air gapping the storage sites to lessen the heat effects. This work utilizes anodic aluminum oxide (AAO) template assisted electrodeposition of cobalt in an external magnetic field to create ordered arrays of perpendicularly magnetized nanowires (MNW) firmly affixed to a substrate. This is achieved by using a custom AAO transferring method and controlling the voltage, pH, and growth conditions during the MNW synthesis. Utilizing an external magnetic field during the MNW growth it was found that the crystalline anisotropy could be oriented parallel to the nanowire length bolstering the shape anisotropy resulting in a partial perpendicular magnetization. The MNW were characterized by Scanning electron microscopy, X-ray diffraction, transmission electron microscopy including precession and holography measurements, and vibrating sample magnetometry to ascertain the MNW physical properties. These properties include nanowire aspect ratios, separation, crystallinity, and magnetization orientation. These results show that with further research this method could create MNW with perpendicular magnetization. The possible applications for these MNW not only include a viable alternative to current magnetic recording media but also biosensors, bio-scaffolding, waveguides, and magneto-plasmonic applications.