Bit shift with ring heads on CoCr and CoCr/NiFe perpendicular recording media

Abstract

Bit shift is a type of distortion of the stored information in a digital magnetic recording system, which, if too large, will result in data loss. This paper compares the bit shift performance of sputtered CoCr (0.5 μm) and sputtered CoCr/NiFe (0.25 μm/0.5 μm) perpendicular magnetic recording media when Mn-Zn ferrite ring heads (gap length = 0.375 μm, track width =37 μm) in contact with the media are used for reading and writing. Bit shift was measured as a function of bit density using zero-crossing, peak, maximum slope, and maximum curvature bit detection schemes. On single-layer media using zero-crossing detection, bit shift becomes severe (20%) at about half the D50 (the density at which the output is half of its maximum value), but using maximum slope detection bit shift does not become severe until about 80% of the D50. These results agree with previous reports (Saito et al., Intermag 1984). On dual-layer media using either zero-crossing or maximum slope detection the bit shift did not become severe until the D50 was reached. CoNi longitudinal media bit shift performance was similar to that of the perpendicular media.