Nobutaka Ihara

Disk substrate deposition techniques for monodisperse chemically synthesized FePt nanoparticle media

Self-assembled FePt nanoparticles hold promise for future ultrahigh-density magnetic recording media because of their high anisotropy and capability to be formed into small and uniform grains. By using a special spin coater, we were able to form a dense array of FePt particles across the entire surface of a 2.5 in. disk substrate. Our method can control the number of layers of FePt nanoparticles. The media deposited with FePt nanoparticles by the spin coater was annealed in a vacuum. We measured read–write properties of the FePt nanoparticle media on a spin stand, and succeeded in detecting a signal of 290 kfci.

L10-FePt nanoparticles in a magnetically isolated state

A novel technique for fabricating a L10-FePt nanoparticle film in a magnetically isolated state is reported. An organic mixture, which stabilizes colloids, inhibits the nanoparticles from forming agglomerations during annealing at up to 800°C, and the resulting film shows the included FePt nanoparticles to be L10 phase and magnetically isolated. Such a film indicates a steep decline in coercivity with the temperature increase whereas the nanoparticles have a large uniaxial anisotropy energy density because of thermal relaxation that corresponds to the particle size.

Magnetic properties of a real FePt nanoparticle system

In this paper, we report a chemically ordered and agglomeration-free FePt nanoparticles system, which is enabled by adding an agglomeration inhibitor. The inhibitor is so effective that gives agglomeration-free status after post-anneal under vacuum, even if it is carried out at 800/spl deg/C. This method therefore revealed magnetic properties of FePt as isolated nanoparticles.