Investigation of High-Speed Solid Contact Induced Demagnetization on - - PowerPoint PPT Presentation

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Investigation of High-Speed Solid Contact Induced Demagnetization on - - PowerPoint PPT Presentation

Dec 06, 2022 270 likes •396 views

Investigation of High-Speed Solid Contact Induced Demagnetization on Perpendicular Magnetic Recording Discs Yuan Ma, Yuliang Liu and David Bogy Computer Mechanics Lab University of California, Berkeley Content 1. Introduction 2.

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Investigation of High-Speed Solid Contact Induced Demagnetization on Perpendicular Magnetic Recording Discs

Yuan Ma, Yuliang Liu and David Bogy

Computer Mechanics Lab University of California, Berkeley

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Content 1. Introduction 2. Staging details 3. Preliminary results 4. Experiment plan 5. Conclusion

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  • 1. Introduction

Two main factors to cause demagnetization are stress and temperature.

Stress induced demagnetization has been studied in much detail with hysitron Temperature induced demagnetization has been studied with heating plate and laser

In HDD, demagnetization and signal loss are sometimes caused by high speed contact between slider and disk, in which process stress and heat are coupled. Aim: To find the weight of the two factors in demagnetization.

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  • 2. Staging details

Steel probe scratch the rotating disc (5400 RPM)

  • n the vena stage.

Ball bearing and lever to control the normal force acting on the probe.

Mdrive N f mg fair Rotation Rotation Ball Bearing Stage movement lever Probe Disc

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  • 2. Staging details

Probe tip: 15-20 µm in radius

Probe tip Probe fixture

Applied contact force: 0-500mN

Measurement of static contact force Measurement of air bearing force

Test results showed that the load is sufficiently larger than the air bearing force.

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Contact time control: Within 30ms

Driven by the actuator motor, the contact can be controlled within 2 revolutions at 5400 rpm.

  • 2. Staging details

Contact time controlled by actuator and string

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  • 3. Preliminary results

OSA scan results to locate the scratch

Scratch on the disc under OSA5100

Scribe scratch

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  • 3. Preliminary results

AFM and MFM scan result

AFM MFM Particles resulted from scratch Change in magnetic field

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  • 3. Preliminary results

AFM and MFM scan result

AFM MFM Hardly visible scratch on AFM with identifiable magnetic change Visible scratch

  • n AFM with

identifiable magnetic change AFM MFM

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  • 4. Experiment plan

 Rewrite magnetization on disks after contact and evaluate the proportion of heat induced demagnetization.  Measure the dynamic friction coefficient of the probe-disk interface.  Prepare data encoded disk to evaluate the degree of data loss after solid contact.  The following questions will be addressed in the experimental studies:

 How to prepare data encoded disks for the experimental study?  How to determine the temperature of the probe tip and contact area under different rotation speeds?  How to exclude the recoverable part of stress induced demagnetization?

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5 Conclusion A high speed solid contact experimental stage is Completed

Contact time and contact load can be adjusted and determined. The Diameter of contact probe is within 20µm.

Preliminary tests showed changes in magnetic signal after scratch

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Thank you!