Development of magnetic nanoparticle recoding media via chemical template assisted self-assembly

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Fabrication technique for ferromagnetic nanoparticles such as FePt alloy array structure via patterned template assisted self-assembly has been developed for possible application to magnetic recording media over 1Tbit/in^2. We tried to chemically synthesize L1_0-FePt nanoparticles by optimizing the synthesis condition in the post-annealing procedure of the fcc-FePt seeds. As a result, partially ordered L1_0-FePt nanoparticles with volume fraction of 50% were successfully obtained under high-temperature and strong reduction conditions without any surfactant. In addition, in order to obtain magnetic nanoparticles with uniaxial magnetic anisotropy with high volume fraction, we have developed the quantitative characterization technique of decomposition rate of Co precursors in the synthesis using IR spectra and successfully synthesized hcp-Co nanoparticles with volume fraction of 70-80% under slow decomposition rate condition.We have also fabricated the mono-layered nanoparticle periodic array structure with highly oriented crystallographic c-axis of the nanoparticles by applying chemical/physical adsorption between nanoparticle and substrate. As a result, electro-chemically modification of the substrate surface using scanning probe microscopy technique has realized selective deposition of FePt nanopaticles, resulting in 0.1 Tdots/in^2 of the FePt nanoparticle dots. Furthermore, by applying di-block co-polymer template substrate, selective deposition of one nanoparticle was realized on one hydrophobic dot. And the c-axis oriented nanoparticle array structure was partially obtained by applying external magnetic field.