Effects of Track-Seeking Motion on the Flying Attitudes of Ultralow Flying Sliders

Abstract

IntroductionA gap flying height of less than 5 nm is required for ultrahigh density recording. For such ultralow flying sliders, the changes in FH during track-seeking motion not only cause signal loss, but also significantly increase the risk of head-disk contact. Moreover, the presence of nanoscale adhesion forces, such as intermolecular and electrostatic forces, adversely increases the FH drop and even causes head-disk impact. In order for a reliable head-disk interface to be maintained, the FH change and contact between the slider and disk must be avoided. Different ABS designs can perform quite differently during the track-seeking process. Therefore, the dynamic track-seeking performance of air bearing sliders is becoming of increasing importance. A better understanding of factors that cause FH change should help improve the ABS design to achieve better track-seeking performance. In this paper, we propose a quasi-static approximation of track-seeking motion. The track-seeking performances of four different air bearing surface (ABS) designs are numerically investigated by the quasi-static approximation and the CML Dynamic Simulator. Results and DiscussionIn order to reduce the computation efforts of track-seeking simulations and quantitatively study the contribution of various factors on the FH change during track-seeking, we carried out a quasi-static approximation of track-seeking motion. Instead of simultaneously solving the generalized Reynolds equation and the equations of motion of a slider at each time step, we solve the Reynolds equation under static suspension loading with consideration of the seeking velocity and HGA inertia at different radial positions during track-seeking. We studied four ABS designs with subambient pressure regions (Fig. 1). ABS I was designed using an optimization algorithm for a nearly uniform 5-nm FH across the disk. The second design labeled ABS II was obtained from a commerical product. The third and fourth designs, named Scorpion III and Scorpion IV, were designed for controlled-FH sliders with thermal and piezoelectric nanoactuators [1],[2],respectively. For a controlled-FH slider, the FH is about 10 nm in the off duty cycle and is reduced to ~2 nm during reading and writing by applying either a current or a voltage to an active element, such as a resistive heating element or piezoelectric material. Fig. 1 shows comparisons of FHs during the corresponding full-stroke seeking loop between dynamic simulations and quasi-static approximations. It is seen that for all the designs the quasi-static method demonstrated good agreements with dynamic simulations. Scorpion III and IV exhibit extremely small FH variations, which can significantly reduce the risk of head-disk contact . Fig. 3 shows the effects of various factors on the FH changes of ABS I seeking from ID to OD. The skew angle change is the dominant factor that causes FH change during track-seeking and the inertia effect accounts for ~12% of the FH change. In order to study the effect of intermolecular and electrostatic...

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