Journal of the Magnetics Society of Japan

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A head combined with a read/write (R/W) gap and a pre-erase gap was adopted for 4-MB flexible disk drives. The reproduced waveform asymmetry due to the permeability of the erase head was analyzed in both recording and reproduction processes. The asymmetry in the recording process is due to the leakage flux from the erase head to the R/W head, and is not increased by decreasing the permeability. The asymmetry in the reproduction process is due to the remanent magnetization in the erase head. The erase field generated by the remanent magnetization was calculated by using the finite element method. When the erase field equals the media coercivity, the reproduced asymmetry reaches a maximum. The asymmetry does not increase when the field is below 18 kA/m using an medium with 48 kA/m coercivity. Therefore, using a low-permeability and low-remanence magnetization material as an erase core is a solution to the problem of decreasing the waveform asymmetry.

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