Micro-patterned high-density magnetic recording media by self-assembly in solution

本报告描述了在溶液中通过自组装工艺制备用于高密度磁记录介质的纳米颗粒阵列。将反胶束技术与磁性纳米粒子的自组装相结合，发现在60℃以下的低温下，制备铁氧体粒子的pH值向较高范围移动，这是采用反胶束技术的最高温度。对于合成磁铁矿或钴铁氧体颗粒，氨水溶液在结晶度和颗粒大小方面优于NaOH溶液。在25~55℃范围内，反应温度对颗粒大小和结晶度没有影响，饱和磁化强度随反应温度的升高而增大。然而，在本研究中得到的各种颗粒在室温下都表现出超顺磁性。在颗粒中添加Co离子可提高5K的矫直力，最大值大于10kOe。然而，Co铁氧体颗粒仍然是超顺磁性的。平均粒径约为10 nm。透射电子显微镜观察和纳米束电子衍射图表明，产物为单晶；透射电子显微镜观察发现，一些平均尺寸为10 nm的颗粒组装在一起，另一些尺寸较小的颗粒没有组装在一起。这一结果表明，大小一致的粒子往往会相互组装。换言之，粒子很可能通过自组装过程以相似的大小进行排序，这一趋势对制造均匀粒子的阵列有影响。利用自组装有机分子对宽度为2 mm、间距为4 mm的颗粒膜进行微图案化，以制备图案化磁记录介质。然而，图案化的质量不如只有有机分子的薄膜。

This report describes the preparation of a nanoparticles array for high-density magnetic recording media by a self-assembly process in a solution. Reverse micelle technique for preparing magnetic nanoparticles and self-assembly for arraying the particles were combined.It was found that pH values for preparing ferrite particles moved to higher range at low temperature below 60℃, which is the maximum temperature to employ the reverse micelle technique. An ammonia solution was superior to a NaOH solution regarding crystallinity and particle size for synthesizing magnetite or Co ferrite particles. While reaction temperature did not influence the particle size and crystallinity in the range from 25 to 55℃, saturation magnetization increased with increasing the temperature. However, all kinds of the particles obtained in this study exhibited super-paramagnetic properties at room temperature. Adding Co ions to the particles increased coercivity at 5 K, and the maximum value was higher than 10 kOe. However, the Co ferrite particles were still super-paramagnetic. Average particle size was about 10 nm. Transmission electron microscope (TEM) observation and electron diffraction pattern with nano-sized beam showed that a single particle was single crystal.TEM observation showed that some particles with the average size of 10 nm assembled and the others with the smaller size distributed without assembling. This result suggests that particles with a uniform size tend to assemble each other. In other words, the particles probably sort themselves with the similar size by self-assembling process.This tendency has an effect on manufacturing the array with uniform particles. Micropatternig of particulate films with the width of 2 mm and the pitch of 4 mm were tried with the help of self-assembling organic molecules in order to fabricate patterned magnetic recording media. However, the quality of the pattering was not as good as that of films of only the organic molecules.