Advanced Micromagnetic Analysis of Write Head Dynamics Using Fastmag

Magnetization and magnetic field dynamics arising when switching a realistic recording head model is studied. The write head design comprises a return pole, yoke, main pole, tapered trapezoidal pole tip, tapered wrap around shield (WAS), and soft underlayer. The analysis was performed using the high-performance micromagnetic simulator FastMag, which is well suited for the write head dynamic problems due to its ability to handle complex magnetic devices discretized into many millions of elements. The head dynamics is considered for different mesh densities, switching data rates, and current waveforms. It is demonstrated that improper discretization may result in a very different magnetization behavior. This is especially pronounced for cases of high switching rates, for which meshes of insufficient density resulted in a completely incorrect behavior, e.g. absence of switching. On the other hand, sufficiently dense meshes resulted in reliable dynamics and switching behavior. Furthermore, magnetization dynamics effects in WAS and their effects on the magnetostatic fields in the media layer were studied. WAS significantly improves the head field gradients in both down- and off-track directions, which is important for high areal recording densities. However, the presence of WAS leads to reduced write fields below the pole tip and to significant undesired magnetostatic fields below the side shields in the media layer. Such undesired fields can be obtained close to the pole tip as well as far from the tip. These phenomena result from the domain wall creation, propagation, and annihilation in WAS due to the switching. The field close to the pole tip can result in adjacent track erasure, while fields far from the tip can lead to far track erasure. The existence of these fields should be accounted for when performing recording system design optimization and analysis.