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

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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