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In Seon LEE Jung Hyuk KOH Taek Dong LEE
With the rapid increase in recording density in recent years, the development of media with high coercivity and low noise has become an important issue in perpendicular as well as longitudinal recording. Compared with the CoCr binary system, the CoCrTa system is more effective in increasing coercivity. The increase in coercivity is due to not Ta segregation but to enhanced Cr segregation at column boundaries caused by Ta addition. When a Ti underlayer with uniform thickness was used, there was no improvement in c-axis alignment of the magnetic layers in CoCrTa and CoCrPt films, although the lattice mismatch of Co ternary alloys with Ti was much reduced compared with that of the CoCr film with Ti. This indicates that there may be no direct heteroepitaxial relationship between Ti underlayer and CoCr alloys at the Ti-Co alloy interface. In the case of the CoCrPt film, perpendicular coercivity increased linearly as Pt content increased up to 10at%. When Pt content was about 13at%, the shape of the M-H loop showed characteristics of domain wall motion reversal, which indicated strong exchange coupling among columns. When Ta content was increased to 4at% in the CoCrPt film, perpendicular coercivity increased and the shape of the M-H loop suggested that the domain wall motion reversal behavior was much reduced. This is thought to be associated with Cr segregation at column boundaries by Ta addition.
Sung Chul LEE Young Wook TAHK Taek Dong LEE
In this work, micromagnetic simulations of writing and reading processes in a perpendicular system including a single pole head and recording media with soft underlayer (SUL) have been performed. The noise contribution from the recording layer increased with increasing grain size distribution of the recording layer but that from soft underlayer remained almost a constant at a given linear density. Details of the noise from the soft underlayer will be discussed. Also thermal decay over a long time scale of the recorded bits was investigated by the Langevin equation and the time-temperature scaling method. It was found that at the linear density of 1058 kfci narrower grain size distribution in the recording layer even in the same average grain size is very important in the point of thermal decay than expectation.