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This paper discusses the role of media damping for a perpendicular recording system that uses a realistic head field and media parameters in a micromagnetic model based on the Landau-Lifshitz-Gilbert formulation for the magnetization dynamics. The modeling approach uses pulsed write fields of varying pulse duration to record footprints of the head on the media. Using a criterion that 95% of the grains are reversed in the footprints, we calculate the field needed to record as a function of pulse duration, i.e., the dynamic coercivity. As shown in a previous paper, we find two distinct regions in the dynamic coercivity plots. The thermally dominated (long time) region can be described by appropriately including the demagnetization effects in the thermal stability factor [K.sub.u]V/[k.sub.B]T. The short time (dynamic) behavior shows a precipitous increase in the required recording field accompanied by an increase in the erase width. The latter effect causes the recording performance to degrade, especially in the short time dynamic regime. The onset of dynamic effects strongly depends on the media damping. In order to achieve high data and high areal density, we need to optimize damping in the recording heads and media. Index Terms--Damping, data rate, dynamic coercivity, Landau-Lifshitz-Gilbert equation, relaxation mechanism.

The paper theoretically examines playback characteristics of a giant magnetoresistive (GMR) head for perpendicular recorded magnetization transitions with a soft underlayer. The magnetic scalar potential, calculated numerically by the finite-element method, is fitted to a simple formula involving geometry-dependent parameters. The reciprocity principle leads to the shape of the single pulse signal. For high permeability of the underlayer the pulse has an error function-type dependence on distance. Within this approximation, the paper derives simple formulas for the pulsewidth [T.sub.50], [D.sub.50], and transition-noise-limited signal-to-noise ratio. Index Terms--Magnetic scalar potential, perpendicular recording, resolution, single pulsewidth, SNR.

This paper describes how dc off-track regions in perpendicular media cause transition shift and track-width broadening. Fields from these regions modulate the applied head field, giving rise to shifts in the positions where the transitions are recorded. The amount of shift depends on the write field gradient at the coercivity, is proportional to the remanent magnetization of the media, and increases with decreasing track pitch. A Poisson solver will he used to obtain the fields and a vector coercivity media model will be used to find the shifts. Index Terms--Neighborhood-induced transition shift (NITS), perpendicular recording, write process.

The effect of thermal fluctuations on the transition of a perpendicular recording system using a micromagnetic recording model is studied. The results highlight that the thermal fluctuation fields must be included in a realistic assessment of the system performance.