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RESEARCH PAPERS

Effect of Intermolecular Forces on the Static and Dynamic Performance of Air Bearing Sliders: Part I—Effect of Initial Excitations and Slider Form Factor on the Stability

[+] Author and Article Information
Vineet Gupta

Department of Mechanical Engineering, University of California, Berkeley, Berkeley, CA 94720vineet@cml.me.berkeley.edu

David B. Bogy

Department of Mechanical Engineering, University of California, Berkeley, Berkeley, CA 94720dbogy@cml.me.berkeley.edu

J. Tribol 128(1), 197-202 (May 05, 2005) (6 pages) doi:10.1115/1.2000269 History: Received February 24, 2004; Revised May 05, 2005

The mechanical spacing between the slider and the disk has to be reduced to less than 5 nm in order to achieve an areal density of 1Tbitin2. Certain physical phenomena, such as those that can be caused by intermolecular and surface forces, which do not have a significant effect at higher flying heights, become more important at such low head-media separations. These forces are attractive for head-media separation as low as 0.5 nm, which causes a reduction in the mechanical spacing as compared to what would be the case without them. Single degree of freedom models have been used in the past to model these forces, and these models have predicted unstable flying in the sub-5-nm flying height range. Changes in the pitch and the roll angles were not accounted for in such models. A 3-DOF air bearing dynamic simulator model is used in this study to investigate the effect of the intermolecular forces on the static and dynamic performance of the air bearing sliders. It is seen that the intermolecular forces increase the level of flying height modulations at low flying heights, which in turn results in dynamic instability of the system similar to what has also been observed in experiments. The effect of initial vertical, pitch, and roll excitations on the static and dynamic flying characteristics of the slider in the presence of the intermolecular forces has also been investigated. A stiffness matrix is defined to characterize the stability in the vertical, pitch, and roll directions. The fly height diagrams are used to examine the multiple equilibriums that exist for low flying heights. Finally, a study was carried out to compare the performance of pico and femto designs based on the hysteresis observed during the touchdown-takeoff simulations.

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Copyright © 2006 by American Society of Mechanical Engineers
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Figures

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Figure 1

Fly height diagram

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Figure 2

Pico slider with a crown of 30 nm and a camber of −5nm. The base recess is 1.397μm.

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Figure 3

Pico slider with a crown of 25.4 nm and a camber of 2.5 nm. The base recess is 2.5μm.

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Figure 4

Intermolecular force magnitude and percentage reduction in fly height at three different radial positions

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Figure 5

Intermolecular force, air bearing force, and total force versus fly height

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Figure 6

Dynamic response without and with intermolecular forces at a disk rpm of 3500

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Figure 7

Dynamic response with intermolecular forces at a disk rpm of 7200

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Figure 8

Fly height diagram for slider shown in Fig. 3

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Figure 9

Pico slider with a crown of 25.4 nm and a camber of 2.5 nm. The base recess is 2.5μm. Femto slider with a crown of 17 nm and a camber of 2 nm. The base recess is 2.3μm.

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Figure 10

Fly height diagrams for pico and femto slider designs at different suspension preloads

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Figure 11

Pico slider with a crown of 25.4 nm and a camber of 2.5 nm. The base recess is 2.5μm. Femto slider with a crown of 17 nm and a camber of 2 nm. The base recess is 2.5μm.

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Figure 12

Fly height diagrams for pico and femto slider designs at different suspension preloads

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