An introduction on electrochemical microsystem technologies (EMT), and the technology of ultra-high-density magnetic recording is reviewed mainly from the viewpoint of EMT as an example is presented in this article. The plated permalloy film has played an important role since 1979 as a key material for the head core of thin film head, ever since IBM shipped the first hard disk drive (HDD) using a thin film head in 1979. Recently, we developed a plated CoNiFe film with a higher Bs (saturation magnetic flux density), which made it possible to shrink the GMR head size to less than 10 μm in yoke length. On the other hand, the size of the magnetic medium is progressively decreasing, and the sputtered magnetic layer such as CoCrPtTa or CoCrPtB possesses such a fine grain structure that the magnetic domain size has become smaller than 100 grains for one bit cell. This is exactly the art of fabrication controlling materials on the atomic scale. At this stage, the perpendicular recording medium becomes important to avoid the diminution of the recorded magnetization against thermal fluctuation. Moreover, in the future the patterned media formed with nanometer-dot arrays will become a candidate for recording densities beyond several hundred GB per square inch. To produce such patterned media, electrochemical processes will become important for mass productivity.
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