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

利用模板辅助自组装技术制备FePt合金等铁磁纳米粒子阵列结构，有望应用于1 Tbit/in^2以上的磁记录介质。我们尝试通过优化fcc-FePt晶种后退火过程中的合成条件来化学合成L1_0-FePt纳米粒子。结果表明，在不添加任何表面活性剂的情况下，在高温强还原条件下，成功制备了体积分数为50%的部分有序L1_0-FePt纳米粒子。此外，为了获得具有高体积分数的单轴磁各向异性的磁性纳米颗粒，我们开发了合成过程中钴前驱体分解速率的红外光谱定量表征技术，在缓慢分解速率条件下成功合成了体积分数为70-80%的六方钴纳米粒子，并制备了单-六方钴纳米粒子。通过在纳米颗粒和基底之间施加化学/物理吸附，形成具有纳米颗粒的高度取向的晶体学c轴的层状纳米颗粒周期性阵列结构。结果，使用扫描探针显微镜技术对基底表面进行电化学修饰，实现了FePt纳米颗粒的选择性沉积，导致0.1 Tdots/in^2的FePt纳米颗粒点。此外，通过应用二嵌段共聚物模板基底，实现了一个纳米颗粒在一个疏水点上的选择性沉积。外加磁场可部分获得c轴取向的纳米粒子阵列结构。

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.