Tsutomu Aoyama

Fabrication and properties of CoPt patterned media with perpendicular magnetic anisotropy

Magnetic dot-arrays with dot diameters of 80 to 1000 nm have been fabricated by patterning CoPt alloy continuous films. All of the fabricated dots had their magnetic easy axes perpendicular to the plane. From MFM observations, dots with diameters of 160 nm and larger had multi domain structures. For the dot-array with 80 nm dot diameter, every dot was observed as a single domain. CoPt dot-array with 80 nm dot diameter showed excellent thermal stability in comparison with conventional longitudinal media and perpendicular media.

Micromagnetic simulations of polycrystalline cobalt islands for patterned media

The magnetization state and the switching field of single domain polycrystalline islands (40 nm/spl times/80 nm/spl times/10 nm) were investigated by micromagnetic simulations. In this work, the crystalline orientations of the grains forming the islands were randomly chosen from a Gaussian distribution, centered along the in-plane short axis of the island. The remanent magnetization was shown to be parallel to the in-plane short axis when the standard deviation /spl sigma/ of the distribution is below 30 degrees. The highest coercivity of an assembly of 100 individual islands was found to be between 3100 and 3700 Oe when /spl sigma/ is as low as 10 degrees and the islands comprise 512 grains. Such an array is promising as recording media for densities beyond 100 Gb/in/sup 2/.

Magnetic patterning of FePt thin films using ion implantation

In this report, the experimental results of implanting different ions to the specified area using a stencil mask and feasibility of fabricating magnetic pattern with a large coercivity difference were shown.