A strong and sharp write-head magnetic field distribution is necessary in order to achieve higher density in perpendicular magnetic recording. The magnetic field of a head medium model was calculated by using a finite element method (FEM) simulator. In studying the head-medium interaction, an FEM simulator was combined with a magnetizing reversal model to realize self-consistent calculation. The magnetic circuit formed by a single-pole head and the soft-magnetic underlayer of a double-layered medium produces an efficiently strong magnetic field. By taking account of the head-medium interaction, a stronger and sharper head field distribution was produced.