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过程制备用于高密度磁记录介质的纳米颗粒阵列。将反胶团技术制备磁性纳米粒子与自组装技术组装磁性纳米粒子相结合，发现在60℃以下的低温下，制备铁氧体粒子的pH值向较高的范围移动，这是反胶团技术的最高温度。氨溶液在结晶度和粒度方面上级NaOH溶液，用于合成磁铁矿或Co铁氧体颗粒。反应温度在25 ~ 55℃范围内对样品的粒径和结晶度没有影响，但饱和磁化强度随温度的升高而增大。然而，在本研究中获得的各种粒子在室温下表现出超顺磁性。Co离子的加入提高了5 K时的矫顽力，最大值超过10 kOe。然而，Co铁氧体颗粒仍然是超顺磁性的。平均粒径为约10 nm。透射电子显微镜（TEM）观察和纳米束电子衍射图谱表明，单个颗粒为单晶; TEM观察表明，部分平均尺寸为10 nm的颗粒聚集在一起，而另一些尺寸较小的颗粒则分布在未聚集的地方。该结果表明，具有均匀尺寸的颗粒倾向于彼此聚集。也就是说，粒子可能通过自组装过程以相似的尺寸进行自我排序，这一趋势影响了均匀粒子阵列的制造。利用有机分子自组装技术，对宽度为2 mm、间距为4 mm的颗粒膜进行了微图案化，制备了图案化磁记录介质。然而，图案化的质量不如仅有机分子的膜的质量好。

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.