Theory of domain dynamics in film heads

The authors recently proposed a variational principle and derived general nonlinear dynamical equations for coupled motions of domains and walls in inductive recording heads. In this report, the yoke region of the core is modeled with a set of parallel 180° walls and domains. Boundary conditions simulate connections to the pole-tip and back gap. To calculate the small-amplitude dynamics, the author Fourier-transforms the motion equations in time and one of the spatial dimensions. Since integration is carried out in advance with respect to the other spatial dimension, the set of linear equations that the computer needs to solve has only one index. This method is inherently more correct and, in the present linear application, more efficient than its predecessors. Illustrative solutions for an input pulse simulating the reading of an ideal transition show how the flux channel broadens with increasing pulsewidth, generally supporting previous conclusions