Modeling study of isolated read-back pulses from keepered longitudinal thin film media using the boundary element method

The magnetic effects of a saturable magnetic keeper layer on the peak amplitude and shape of isolated read-back pulses from longitudinal thin film media were modeled as 2-dimensional magnetostatic field interactions using the boundary element method. The model assumes a standard thin film head and fly height of a 50% slider, a saturable NiFe keeper, and a perfectly sharp recorded transition in high-capacity longitudinal thin film media. Isolated pulses calculated from the model show that the keeper increases the peak amplitude (55%), decreases the half-height pulse width (46%), introduces pulse shape asymmetry, and eliminates undershoots from pole edges. The pulse shape is found to be very sensitive to changes in both the head-bias current and the head-disk spacing