Tracking issues in high-density patterned media storage

In this work, a 3D extension to the reciprocity integral which permits a thorough investigation of how medium characteristics, i.e. thickness, soft-underlayer (SUL), island shape, size as well as the across-track GMR head dimensions affect the readout waveform, is studied. This model is used to study the effects of track misregistration (TMR) and the effect that island distribution has on the replay signal and channel performance in patterned media storage systems. A GMR replay head of sensor width 40 nm, sensor length 8 nm, and shield-to-shield separation 32 nm has been assumed. From the modeling parameters adopted, the presence of adjacent tracks can have a significant effect on the shape of the replay waveform of the main data track. In addition, the increased signal due to TMR can be clearly seen where 10 nm tracking error has been introduced. The channel performance worsens considerably with TMR upon introduction of adjacent tracks. A hexagonally packed patterned array offers much improved channel performance over a rectangular array, even with TMR present.