Research on ferrite thin film with isolated small and pillar like structure for high density HDD medium

尽管现在市场上有垂直磁记录系统，但硬盘驱动器(HDD)系统中的高密度记录仍然是关键问题。用于下一代的记录介质必须是分立型或图案化介质类型，以获得大于每平方英寸1万亿比特的超高记录密度。磁性颗粒必须很小，才能降低介质噪声。此外，颗粒必须被隔离。在本研究中，我们尝试了用纳米点晶化的方法来制备纳米点阵列式的钡铁氧体薄膜。室温下制备的Ba-Fe-O薄膜为非晶态，无磁化。在硅片上沉积的Ba-Fe-O薄膜可在700℃左右晶化，并显示出磁性。为了降低钡铁氧体薄膜的晶化温度，本研究对几种底层材料进行了研究。结果表明，Pd-Pt混合合金底层有利于降低衬底温度和…更多非常小的粒子。此外，还研究了Al膜作为非晶态钡铁氧体薄膜的底层。Al底层上的非晶态Ba-Fe-O层在650℃左右即可晶化，比底层硅的晶化温度低50℃。我们知道，Al-Si合金是一种相分离材料，在硅基中合成了纳米级的铝点。尝试利用Al-Si作底层材料制备具有纳米点状结构的钡铁氧体。在250℃的衬底温度下，通过相分离的方法可以制备出自组装的Al纳米点阵，然后在室温下沉积多晶的Ba-Fe-O薄膜，并在650℃进行后处理，测得的磁化强度与Al的含量相对应。这意味着铝点上的钡铁氧体层只能晶化，而硅基上的其他部分仍然是非晶态的，没有磁化。由于分辨率的限制，目前还不能确定是否制备了纳米点钡铁氧体薄膜。M曲线表明，磁性颗粒分离，交换耦合减弱。综上所述，提出了利用自组装Al-Si衬底制备图案化介质的新技术。较少

High density recording in hard disk drive(HDD) system is still key issue even though a perpendicular magnetic recording system is now on the market. The recording medium for a next generation must be discrete type or patterned media type to attain an ultra high recording density greater than one tera bits per square inch. The magnetic grains must be small to reduce the media noise. Furthermore, the grains must be isolated. In this study, nano-spot crystallization for barium ferrite thin film has been tried to prepare the nano-spot array film of barium ferrite. The Ba-Fe-O films deposited at room temperature is amorphous and has no magnetization. The Ba-Fe-O films deposited on silicon wafer can be crystallized at around 700 C and show magnetic properties. In this study to lower the crystallization temperature for barium ferrite thin film, several kind of under layer materials were examined. As a results Pd-Pt mixed alloy underlayer is suitable for lowering the substrate temperature and … More very small particle. The Al film was also examined as an under layer for amorphous barium ferrite thin film. The amorphous Ba-Fe-O layer on Al under layer can be crystallized at around 650 C. This is 50 C lower than that for silicon under layer. It is know that Al-Si alloy is a phase separate material and nano-sized Al spots are synthesized in silicon matrix. It was tried to prepare barium ferrite with nano-spot like structure using Al-Si under layer. A self assembled nano dots array of Al can be created by phase separation at the substrate temperature of 250 C. Then ampourphous Ba-Fe-O films were deposited at room temperature and post-deposition annealed at 650 C. The measured magnetization is corresponding to Al content. This means that barium ferrite layer on Al spot can only be crystallized and other parts, which are on silicon matrix, are still amorphous and no magnetization. Due to the resolution limits, it is not yet confirmed that nano spot barium ferrite film was prepared. The delta M plots show that the magnetic grains are separated and exchange coupling is weakened. In conclusion, new technique to prepare a patterned medium using self assembled Al-Si under layer. Less