Simulation of the perpendicular magnetic recording process

Abstract

This thesis describes a simulation modelof the complete perpendicular magnetic recording process, from write current to readback voltage. Gontradictory to most models published in literature, it is neither analytical nor iterative. In the model of this thesis, the actual physical process is piecewisely linearized during every stage of recording. Extensive attention is paid to the influence of the so-called effect, caused by the presence of a head and a keeper layer in the vicinity of a magnetized recording layer. Part I gives an introduction to the problem and to the topic of image charges. The assumptions determining the validity of the model are described and accounted for. Also, a theoretical derivation concerning the switching criterion, the level in the recording layer at which self-consistency is assumed, is given. In part II, the actual model is set up. First, the recording of a single magnetization reversal in a DG pre-magnetized recording layer with no head-to-medium motion is analyzed and modeled. Then, the recording layer is shifted along the activated head, which causes a relaxation of the original magnetization distribution. This part of the process, so far predominantly neglected in literature, is described in detail. Also, the influence of a varying head field is investigated to complete the modeling of the write process. Finally, the readback process is modeled using the well-known theorem of reciprocity. The effects of variations of the model's parameters are described in part III. The image-charge effect is treated in a quantitative manner and the influence of the obliquity of the recording layer's intrinsic hysteresis loop is investigated. Also, the influences of the bit density and the head field to coercive field ratio are described. Finally, the thicknesses of the recording layer and the air gap are varied to find that, as expected, the air gap should be chosen as small as possible. Some mathematical derivations concerning demagnetizing fields, image-charge fields and a conformal mapping have been put into appendices completing the thesis.