Effect of thin-film disk texture on magnetic recording signals

Abstract

The effect of texturing on the readback signal of Co-alloy thin-film disks is investigated. Instantaneous pulse area (PA) traces, representative of the magnetic signal strength, and instantaneous pulse width (PW,,) traces, indicative of the transition resolution, are measured. The low-frequency, "twice-around" modulation is removed from these traces. The resulting PA fluctuations are small; the PW fluctuations are larger and closely correlated to the texture. Calibration of PW vs flying height allows comparison of the texture-induced head clearance modulation and the actual disk surface roughness. The texture causes signal resolution (PW) noise which, for these head/disk combinations? is predominantly due to the spacing loss variations during the readback process. The write process and any texture-related H, or it-i/ fluctuations appear to contribute negligibly.

In situ ultra-high resolution magnetic imaging

“…For example, defects and scratches in the medium can be easily characterized given an imaging technique with high enough resolution [1]. The readback process in a HDD can be interpreted as comprising three distinct components: the input magnetization, the multi-dimensional GMR head response (kernel), and the resulting readback voltage.…”

“…Applying the Karlqvist head model and the reciprocity formula for MR heads, (1) the head response to an arctangent transition can be approximated by a Lorentzian [2]. This formula states that the flux sensed by the MR element at the air bearing surface (ABS) is the convolution of the head field function and the magnetization of the media.…”