Activation volume and correlation to media noise in high-density longitudinal recording media

The activation volume (V_a) and its correlation to media noise in high-density longitudinal recording media are investigated. Magnetization decay is observed to be non-linear with ln(t) for the media studied, and the necessity for using a correct method for estimating a fluctuation field is emphasized. The activation volumes are shown to increase with decreasing reversing fields and the values of V _a at low fields (of a few hundred Oe) are significantly higher than those at the coercivity. Thus, the collective behavior of the magnetic grains is influenced not only by the intergranular interactions but also by the stray fields. The media noise of different media is correlated to the V_a values at low fields