Hiroshi Ikekame

Computer simulation of magnetization switching behavior in high-data-rate hard-disk media

We have investigated magnetization switching behavior in high-data-rate hard-disk media by micro-magnetic simulation. We found that the remanence coercivity measured by a short-pulse-field depended on the field-pulse shape. The time integration of external field over the remanent coercivity for a long-pulse-field, namely switching force integration (SFI), was an essential factor for the switching. We also found that the optimum writing field, H/sub w/ must be increased by only 0.4 kA/m per MB/s independent of the linear recording density. Overwrite (OW) value decreased by 1 dB per percentage point of H/sub w/ and did not depend on the data-transfer rate. The recording characteristics at high data transfer rates were not degraded if only a writing field of H/sub w/ was applied to the film. The simulation results were consistent with the results of read/write experiments especially OW characteristics up to 80 MB/s.

Degradation of recording performance in high-speed recording

Effects of dynamic coercivity on recording performance at write frequencies of 10-250 MHz and medium velocity of 20-50 m/s were investigated. It was found that degradation of signal-to noise ratio and roll off characteristics in high-speed recording is extremely small, and degradation of nonlinear transition shift is mainly due to the rise time of the magnetic field in the write head. Moreover, overwrite characteristics degrade significantly because of dynamic coercivity effects.