Effect of write current waveform on magnetization and head field dynamics of perpendicular recording heads

Abstract

The continuing advances in magnetic recording density and data rates require an ever more detailed understanding and control of the dynamic processes in magnetic write heads, recording media, and read heads. As the typical dimensions of the write pole of single pole-type perpendicular recording heads shrink to about 100 nm and data-rates exceed 1 GBit/s the dynamic magnetization processes in the write pole and its interaction with the SUL and the return pole become very important. We have used a large scale finite element micromagnetics model to study the head field dynamics of single pole-type perpendicular recording heads. The model includes a fully discretized write pole, return pole, and soft underlayer, which allows a realistic assessment of the magnetization dynamics in the writer and the calculation of the head field as a function of time. We have studied the effect of current rise time, current overshoot, overshoot duration, and head geometry (yoke length, coil position) on the magnetization dynamics in the write pole and the head field. Both, larger overshoot and shorter current rise times can reduce the head field switching time significantly. The shorter current rise time has been found to have considerably stronger effect. The shorter current rise time is more effective in improving the head response, because the magnetization in the write poles does not respond to the change in coil current until the coil current changes its polarity and generates a field, which can reverse the magnetization of the write head. In addition, it has been found that a short yoke structure and the coil close to the air bearing surface can improve the head field response because it shortens the distance between the head, which is directly excited by the coil, and the pole tip, where the magnetization generates the write field. Thus, in order to build high performance perpendicular recording heads, which are capable of writing high coercivity media at high data rates, a carefully optimized design is required, which also considers the effects of the write current waveform on the head field dynamics presented in this paper.