Medium noise in longitudinal thin film disk media above 20 Gb/in2

Medium noise is the dominant noise in ultrahigh density disk recording systems. The peak, width and jitter noise are analyzed by micromagnetic simulations. Four different media, with a fixed grain size of 135 Angstrom and a coercivity of 2900 Oe, are chosen for medium noise analysis. The linear recording density is increased from 340 KFCI (Kilo flux-changes per inch) to 750 KFCI, while the area density goes up from 14.3 Gb/in(2) to 31.5 Gb/in(2). The peak-amplitude noise is studied by the distribution of the peak magnetization M-p in each bit. The distribution of M-p develops from a delta-function around the remanence M-r at low densities to a flat distribution at extremely high densities. It is found that the transition a-parameter is no longer proportional to the square root of M(r)delta, as given in the William-Comstock approximation. The peak-jitter noise in the read back voltage is analyzed by the percentage of the transition jitter in a bit length.