Magnetic hard and soft phases CoCrPt-SiO 2 thin films were developed to fabricate exhange coupled composite (ECC) media. Domain wall nucleation and propagation from the soft regions to the hard regions in the composite grains was found to be the switching mechanism in the ECC media. ECC media on the disk substrate with soft underlayer was fabricated. Interlayer thickness dependence of saturation field and domain wall length in CoCrPt-SiO 2 soft layer suggested that domain wall nucleation and propagation in ECC media. Spin-stand testing showed more than a six-times reduction of saturation writing current and more than a 10 dB increase of total signal-to-noise ratio (SNR) for ECC media. Time decay results of readback signals indicated that there is no thermal stability problem for ECC media. The roll-off curve of ECC media showed the same SNR level as a state-of-art reference perpendicular media targeted around 200 Gb/in 2 . With further optimizations, areal densities beyond 1 Tb/in 2 seem achievable for ECC media.
We designed and fabricated a composite magnetic recording medium with exchange decoupled magnetic grains that consist of two vertically exchange-coupled magnetic regions (one is magnetically soft and one is magnetically hard) as an approach to alleviate the writing field limitation of perpendicular magnetic recording heads. A nonmagnetic layer with different thickness was put between the hard and soft layer to tune the exchange coupling. With proper coupling, significant drop of the coercivity field was observed for this composite medium while still maintaining good thermal stability. Better recording performance was obtained for such medium compared to perpendicular and longitudinal medium. The results have proved the possibility of fabricating a writable recording medium having an ultrahigh magnetic anisotropy constant (Ku) value.
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