Head-disk interface considerations at 10-nm flying height

Bit patterned media (BPM) is considered as a revolutionary technology to enable further increase of areal density of magnetic recording beyond 1 Tbits/in2 [1]. Implementing BPM technology, however, significantly increases the complexity of the recording process, but also poses tremendous tribological challenges on the head-disk interface (HDI) [2]. One of the major challenges facing BPM is touchdown detection by thermal flying-height control (TFC), in which a minute heater located near the read/write transducers is used to thermally protrude a small portion of the slider into contact with the disk, and the contact is then detected by directly or indirectly measuring the friction, temperature rise or vibration caused by the contact [3]–[7]. Most recording heads rely on touchdown detection to achieve a desired flying height (FH), which approaches sub-1-nm regime for many of today’s commercial drives. As a result sensitive and accurate touchdown detection is of critical importance for a reliable head-disk interface by reducing contact duration and unnecessary interaction between the slider and the disk. However, the impact of touchdown on the mechanical robustness of the media has not been properly studied.

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Head-Disk Interface Issues for Near Contact Recording

ASME 2001 Symposium on Nanotribology and Nanotechnology for 1Tbit/in2 ◽

10.1115/trib-nano2001-105 ◽

2001 ◽

Cited By ~ 4

Author(s):

R. H. Wang ◽

V. Raman ◽

U. V. Nayak

Keyword(s):

Ambient Pressure ◽

Disk Drive ◽

Flying Height ◽

Head Disk Interface ◽

Disk Interface ◽

Magnetic Spacing ◽

Wear And Corrosion ◽

Disk Lubricant ◽

Contact Recording

Abstract As the magnetic recording density increases towards hundreds of Gb/in2, both the magnetic spacing and head-disk clearance decrease to < 10 nm. By one estimate, the magnetic spacing for 1 Tb/in2 is about 6 nm and the read width is ∼ 30 nm. There are at least two different approaches to achieving this. The first one is an extension of the traditional flying interface and the second is contact recording. In the former case one needs to be concerned about maintaining adequate clearance both at sea level and at higher elevation whereas in the latter case the wear and corrosion of the heads and disks may pose major challenges. In the flying regime, an accelerated test to assess the relative integrity of the head-disk interface is described here. This is accomplished by monitoring the acoustic emission, capacitance or friction between the head and the disk as the ambient pressure is reduced. The pressure at which an abrupt change in the above signals takes place is called take-off pressure (TOP). This is also known as altitude avalanche measurement. With this method it is possible to compare different disk and head designs at the full velocity of the slider. We present results correlating the TOP with disk roughness and the influence of disk lubricant. An example of how head-disk interference takes place in a disk drive will be given for an experimental 10 nm flying slider. The effects of radial flying height profile, take-off height of the disk, and the disk curvature on mechanical spacing are presented. The results of changes occurring on the air bearing surface and the disks after long term flyability test are discussed.

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Simulation of Contact at Head and Multilayer Disk Interface Under Quasi-Static Condition

ASME 2016 Conference on Information Storage and Processing Systems ◽

10.1115/isps2016-9607 ◽

2016 ◽

Author(s):

Ao Hongrui ◽

Han Zhiying ◽

Zhang Kai ◽

Jiang Hongyuan

Keyword(s):

Normal Load ◽

Static Condition ◽

Flying Height ◽

Lubricant Layer ◽

Magnetic Storage ◽

Multilayer Thin Film ◽

Head Disk Interface ◽

Principal Stresses ◽

Disk Interface ◽

Von Mises

The reduction of head-media separation (HMS) results in a decreased flying height. Consequently, the contact probability between the slider and the lubricant layer or hard overcoat surface on the disks will increase greatly. Therefore, investigating the contact stress of the disk is vital for improving the reliability of the head disk interface. In this study, a rigid hemisphere sliding over a multilayer thin film half-space is implemented to simulate the contact between the recording slider and the magnetic storage multilayer disk under the quasi-static condition. The effects of different parameters such as normal load, friction coefficient and radius of slider on the von Mises, shear and principal stresses in the multilayer system are analyzed by using finite element method (FEM).

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Characterization of light contact in head disk interface with dynamic flying height control

Microsystem Technologies ◽

10.1007/s00542-011-1253-7 ◽

2011 ◽

Vol 17 (5-7) ◽

pp. 1225-1230 ◽

Cited By ~ 12

Author(s):

Jianfeng Xu ◽

Gang Sheng

Keyword(s):

Flying Height ◽

Head Disk Interface ◽

Disk Interface ◽

Height Control

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Effect of particulate contamination on the friction and wear of a magnetic head-rigid disk interface

Proceedings of the Institution of Mechanical Engineers Part J Journal of Engineering Tribology ◽

10.1243/1350650001543368 ◽

2000 ◽

Vol 214 (5) ◽

pp. 493-505 ◽

Cited By ~ 9

Author(s):

S Chandra ◽

B Bhushan

Keyword(s):

Failure Mechanism ◽

Friction And Wear ◽

Particle Concentration ◽

Damage Mechanism ◽

Flying Height ◽

Head Disk Interface ◽

Magnetic Head ◽

Disk Interface ◽

Particulate Contamination ◽

Rigid Disks

Particulate contamination studies were carried out with laser-textured and mechanically textured magnetic rigid disks and nanosliders. The effects of particle concentration and its size, particle material, duration of exposure to contamination, interface speed and disk textures were studied. The head-disk interface (HDI) durability increased as particle concentration decreased. The effect of different hard-particle materials was attributed to how easily it can form agglomerates. Data indicate that limited-time exposure to a class 10 000 environment will not deter tribological performance of the HDI. In a contaminated environment, head flying in the data zone exhibited higher durability than that in the-lase textured zone. However, the mechanically textured disk and the data zone of laser-textured disks showed comparable durability in the presence of contamination. The HDI damage mechanism and pattern changed as the disk speed changed. A failure mechanism to show how the airborne particles interact with the interface is presented. The effects of the HDI geometry, flying height, pitch angle which controls the air flow pattern govern the failure mechanism in the flying mode.

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Analysis of Contact Deformation and Stiction Between Textured Disk and Textured Slider

Journal of Tribology ◽

10.1115/1.1308006 ◽

2000 ◽

Vol 123 (2) ◽

pp. 350-357 ◽

Cited By ~ 13

Author(s):

Mingwu Bai ◽

Koji Kato

Keyword(s):

Physical Model ◽

Contact Area ◽

Surface Texture ◽

Flying Height ◽

Loading Conditions ◽

Contact Deformation ◽

Head Disk Interface ◽

Disk Interface ◽

Recording Density ◽

Texture Parameters

To meet the ever-increasing magnetic recording density, the hard disk industry is focusing on reducing flying height. Texturing the slider surface to reduce the head–disk contact area is one of the most challenging and promising techniques in the current industry. In this study, a mathematical–physical model based on an extension of the Greenwood–Tripp model is proposed for predicting and analyzing the contact deformation and stiction between both textured disk and slider. The contact deformation and stiction of the head–disk interface is analyzed in considering surface texture parameters, lubricant properties, and loading conditions.

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On the Thermal Behavior of Giant Magnetoresistance Heads

Journal of Tribology ◽

10.1115/1.1308005 ◽

2000 ◽

Vol 123 (2) ◽

pp. 380-387 ◽

Cited By ~ 34

Author(s):

B. K. Gupta ◽

Kenneth Young ◽

Sameera K. Chilamakuri ◽

Aric K. Menon

Keyword(s):

Thermal Expansion ◽

Giant Magnetoresistance ◽

Close Agreement ◽

Mechanical Performance ◽

Single Layer ◽

Flying Height ◽

Head Disk Interface ◽

Disk Interface ◽

Atomic Force ◽

Differential Thermal Expansion

The magnetic/mechanical spacing between the transducer and the disk significantly decreases due to thermal expansion of pole tips at stressed high temperature and high humidity tests. The protruded pole tips and alumina overcoat can cause head/disk contacts, resulting in thermal asperities and pole tip damage. The damage at the head–disk interface due to protruded pole tips and alumina overcoat may degrade the drive mechanical performance when flying height is below 10 nm. In this study the change in pole tin recession (PTR) with temperature and current in the writer coil, are measured using an optical profiler and an atomic force microscope for heads having a stack design with single and dual layers of writer coils. The pole tips protrude above the ABS surface by 3–4 nm when the temperature of the head is raised by 50°C. Heads with a single layer of writer coils exhibit significantly lower thermal PTR than those with dual layers of coils. The ABS profiles at elevated temperature generated using the finite element modeling of the differential thermal expansion of various layers in the head stack are in close agreement with the measured profiles. The thermal PTR and alumina overcoat protrusion can be reduced by optimizing the thermal expansion coefficient of the alumina basecoat and overcoat, the height of the head stack, and by replacing alumina by SiO2 and SiC.

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