An Examination of Read Pulse Slimming, in Digital Magnetic Recording Using Double Step Write Current Shaping

The effectiveness of read pulse slimming method by double step write current shaping, reported by Jacoby, is examined in detail. In this method, each transition of write current, I_ω is preceded and followed by a minor transition, I_e of oppsite polarity. AC bias current, I_b is added to linearize the write process of a medium. The half width W_<50> and amplitude E of isolated read signal are observed over a wide range of I_ω, I_e and I_b. Flux reversal density characteristics of read amplitude for all 1's pattern, and overwrite erase rate are also examined. The results can be summarized as follows : 1) The value of W_<50> can be reduced to be about 60% of non-shaped read pulse, by setting I_ω=0.5 I_s (I_s : medium saturation current) I_b=0.75I_s and Ki=I_e/I_ω=0.8 2) For the range of above setting value of I_ω, I_s and Ki, the flat portion of density characteristics is widened to be about twice the value for non-shaped saturation recording. 3) Overwite erase rate becomes worse to be about -20dB or less and this is a weakness included in this method.