Partitioning of the perpendicular write field into head and SUL contributions

We perform multi-scale finite element simulation of the write process in perpendicular media. The Landau-Lifshitz Gilbert equation is solved simultaneously for the head, the data layer, and the soft under layer during the motion of the head. All magnetostatic interactions between head, data layer and soft underlayer (SUL) are concurrently taken into account. This fully integrated recording model enables a detailed analysis of the head field as seen by the media grains. The effects of the media permeability onto the saturation of the soft underlayer and the head pole tip are an inherent part of the simulation model. In this paper, we focus on the time dependence of the different contributions to the total head field, which is composed of the field generated by the pole tip, the field generated by the head, and the self-demagnetizing field of the data layer. Besides the magnetic properties, the only input for the simulations is the current profile for the coil excitation and the head velocity. The head field dynamics is calculated from the induced magnetization processes within the head, the data-layer, and the soft underlayer. Domain wall motion within the yoke of the head, vortex motion within the pole tip of the head, and large-area magnetization processes in the soft underlayer cause a lag of the head field behind the current.