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

Abstract

Abstruct -The magnetic effects of a saturable magnetic keeper layer on the peak amplitude and shape of isolated readback 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 highcapacity 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. ' Fig. 1 Flux from a single transition through the thin film head.

Keepered Media Recording: super-resolution for magnetic recording

“…Study of the large-signal read process involves direct calculation of the flux in the head while including nonlinear saturation effects in the keeper layer. Loven, et aI., [9] used a non-linear boundary element method to study readback pulses from isolated step transitions of magnetization in a longitudinal recording medium. They found that the pulse sharpening of keepered recording observed by Gooch, et aI., can be accompanied by time-shifts and time asymmetries.…”

“…Interest was revived at various times from 1990 to 1996 with a number of companies pursing the technique as an alternative to MR head technology [7,8]. In academia, the University of Minnesota has maintained an ongoing activity in both the theory and the implementation of keepered recording [9,10]. Recent work by Wilson et al at Stanford University has focused on overcoming some of the nonlinear distortions inherent in the technique [11].…”

“…Figure9. Isolated pulses for MR readback of keepered media where the keeper layer is placed below the hard recording layer.…”

Design optimization of a non‐linear magnetic media system using finite element analysis and Taguchi method

“…In the quest for increasing the areal densities of rigid and flexible magnetic recording media, a keepered magnetic recording media was proposed (Loven, 1994; Coughlin, 1996, 1997; Reed, 1996; Wood, 1997). It was made essentially by adding a thin layer of soft‐magnetic material (keeper layer) above (or under) the hard‐magnetic storage layer.…”