A method to estimate pole tip protrusion in recording heads

In order to support increasing recording density, the flying height of magnetic recording sliders continues to decrease. At flying heights less than 10 nm, thermal protrusion induced by write current and operational temperature of the drive is a significant fraction of the total head-disk spacing. The experimental method described provides a means to estimate dynamic PTP induced by current and temperature. Finite element commercial software, ANSYS is utilized to solve the steady state multi-physical problem in the write process. By making differential measurements of head topography after maximizing cross-correlation, the effect of dissimilar materials on the measured static protrusion is eliminated. By comparing dynamic PTP with static PTP measured by optical profilometry, it is observed that cooling due to airflow and proximity to the disk during flying are significant in reducing the net protrusion. Experimental and modeling results are in good agreement in the estimate of this cooling effect. For the recording head evaluated in this study, dynamic write induced PTP is approximately 57% lower than static PTP at 25 °.