The effect of a trailing shield for perpendicular write heads

Abstract

The effect of a magnetic trailing shield located in close proximity of the pole tip for a perpendicular write head has been studied in a perpendicular recording system. For a 150nm wide write pole, the write field gradient is improved yielding a 40% decrease in jitter and 2.2dB increase in the signal-to-noise ratio (SNR). As the pole width is narrowed further, modeling and experiments show that the trailing shield leads to a tradeoff between maintaining a high write field (writeability) and achieving an optimal write field gradient (jitter). For a 70nm writer, the addition of a trailing shield results only in a small 0.5dB SNR gain despite a 25% decrease in jitter as a result of the concomitant loss in writeability. The latter results in an increased dc noise and becomes more significant with trailing shield throat thickness.

The transition from longitudinal to perpendicular recording

“…As rule of thumb, the gap g should be about the same has the head-to-keeper spacing h KS [43]. Practical implementations and theoretical aspects of shielded heads have been discussed in [40,43,[45][46][47][48][49]. Since some of the flux generated by the main pole is sucked away by the shield, the SUL can be made somewhat thinner [48].…”