Magnetization dynamics of planar writers

We have developed a micromagnetic finite-element method (FEM) to treat a whole write head structure as a micromagnetic model, and it is utilized to study the magnetization dynamics and head field of a planar writer. As the head has a domain structure, the leakage field differs from what is calculated by a conventional FEM except for the gap region, and it can induce some adjacent track erasure (ATE) problems in the case of high write currents. This leakage field comes from the shoulder of the bottom yoke pedestal and the sidewall of the upper pole. A conventional FEM for electromagnetic eddy-current field does not show much time delay of the head field rise in core sizes of 10 μm or below. On the other hand, the head field cannot follow the write current waveform perfectly, and shows time delay by the micromagnetic FEM analysis. This indicates that the delay mainly no longer comes from eddy-current effects but magnetization dynamics of the gyromagnetic precession, damping, and flux conduction. Furthermore, the head field rise time is affected by the damping constant, material, yoke length, and pole-tip dimension.