Soft Particle-Induced Magnetic Erasure Without Physical Damage to the Media

[+] Author and Article Information
M. Roy

 Seagate Technology, 7801 Computer Avenue South, Bloomington, MN 55435

J. L. Brand

 Seagate Technology, 7801 Computer Avenue South, Bloomington, MN 55435mallika.roy@seagate.com

J. Tribol 129(4), 729-734 (Apr 20, 2007) (6 pages) doi:10.1115/1.2768071 History: Received April 24, 2006; Revised April 20, 2007

With ever increasing areal density, interactions of particles with a head-disk interface become an ever more important factor impacting the drive reliability. Although particles trapped between the head and the disk could induce mechanical damage to the media resulting in permanent loss of data, data loss has also been observed without any obvious signs of physical damage to the media. We devised a component-level test to study this mode of data erasure on both glass and aluminium media. Our data indicate that the frictional heating associated with contact force between the particle and the disk could lead to permanent loss of data. In addition, we performed investigations to study the impact of air bearing design features, load/unload mechanism, and particle number density on the head disk interface.

Copyright © 2007 by American Society of Mechanical Engineers
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Grahic Jump Location
Figure 1

FESEM image of a cluster of particle on the disk. In this image, the largest particle is 8×12μm. There are a couple of ∼3μm. particles, 5μm. particles, and around 20 particles <1μm.

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Figure 2

Schematic of the slider. The areas in white show the ABS. The light gray areas are recessed by 0.25μm from the ABS. The dark areas are recessed ∼4μm below the ABS. The leading edge recessed corner and the lateral trench are highlighted as the areas where particles accumulate.

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Figure 3

Typical data; (a) Image of the disk with coherent data written on it, (b) image of the same disk, showing the data loss after 100 cycles of L/UL and seek. The erasure occurred at a skew of ∼0deg. (c) Result of subtracting image (a) from image (b).

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Figure 4

(a) The right- and left-hand images respectively show the magnetic force microscopy (MFM) and atomic force microscopy (AFM) images of damaged location. The alternate high and low frequency data in the MFM image is represented by the striped and uniform pattern respectively (b) magnified AFM and MFM images of the erased site. (c) Spectral analysis of the MFM data of the unerased site and (d) spectral analysis of the MFM data of the erased site.

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Figure 5

Normalized coercivity (normalized to Hc at room temperature) of the media as a function of temperature

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Figure 6

Number of remaining particles on the disk as the sweep cycle is increased. The size is based on the intensity of the signal from the OSA. The particle size reported by the OSA is based on calibration with latex beads.

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Figure 7

Dark field image (at a magnification of 500X) of a typical head showing the particles trapped in the lateral trenches that appeared to be rolled up. The head was subjected to 100 cycles of L/UL on a disk that was injected with 600 particles.



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