A Method to Measure the Media Lubricant Loss After HAMR Recording

2016 ◽  
Author(s):  
Dongbo Li ◽  
Shaomin Xiong ◽  
David Braunstein ◽  
Xingcai Guo ◽  
Sripathi Canchi ◽  
...  
Keyword(s):  
Hard Disk Drives ◽  
Areal Density ◽  
Disk Surface ◽  
Thickness Variation ◽  
Laser Exposure ◽  
Lubricant Thickness ◽  
Thickness Change ◽  
Force Microscopy ◽  
Magnetic Switching ◽  
The Media

Heat assisted magnetic recording (HAMR) is anticipated to increase the areal density in hard disk drives to multiple Tb/in2. During HAMR recording, as a near filed laser light heats the media to the temperature above Curie point to assist magnetic switching, the lubricant that is typically applied to the disk surface will be under an intensive thermal stress, which will lead to the lubricant desorption and/or decomposition, and frequently accompanied with the underneath carbon overcoat (COC) graphitization and oxidation. Due to the optical properties change of the COC at such a high temperature, the traditional optical techniques are not appropriate to measure the lubricant thickness post HAMR recording. In this paper, we introduce a new method based on atomic force microscopy (AFM) in different imaging modes to detect the lubricant and also COC thickness change as a result of laser heating with a vertical resolution at the angstrom scale. Using AFM in a soft tapping mode, we can also characterize the lubricant thickness variation with time after laser exposure, which enables the measurement of the lubricant reflow kinetics on HAMR media.

A Scanning Method to Study the Influence of Roughness, Microwaviness, and Lubricant Thickness Variation on Slider Dynamics

2005 ◽  
Author(s):  
Maik Duwensee ◽  
Bernhard E. Knigge ◽  
Peter Baumgart ◽  
Frank E. Talke
Keyword(s):  
Acoustic Emission ◽  
Disk Surface ◽  
Flying Height ◽  
Thickness Variation ◽  
Emission Measurement ◽  
Lubricant Thickness ◽  
Scanning Method ◽  
Displacement Maps ◽  
Acoustic Emission Measurement ◽  
A Current

Flying height modulation maps and microwaviness maps are obtained by using laser Doppler vibrometry (LDV) and acoustic emission (AE) transducers which are moved radially over the complete disk surface. The sensitivity of the acoustic emission measurement is improved by applying a current to the write element, thereby increasing pole tip protrusion. Disk and slider displacement maps are obtained using a radially scratched disk. Acoustic emission maps are presented for a scratched disk and for a non-scratched disk. For the non-scratched disk, AE maps are obtained with an inactive and active write element.

Lubricant Depletion and Disk-to-Head Lubricant Transfer at the Head-Disk Interface in Hard Disk Drives

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
Rohit P. Ambekar ◽  
David B. Bogy ◽  
C. S. Bhatia
Keyword(s):  
Hard Disk Drives ◽  
Areal Density ◽  
Disk Drives ◽  
Lubricant Thickness ◽  
Lubricant Transfer ◽  
Disk Interface ◽  
Slider Air Bearing ◽  
Disk Lubricant ◽  
The Stability ◽  
Lubricant Performance

As the head-disk spacing reduces in order to achieve the areal density goal of 1 Tb/in.2, the dynamic stability of the slider is compromised due to a variety of proximity interactions. Lubricant pickup by the slider from the disk is one of the major reasons for the decrease in the stability as it contributes to meniscus forces and contamination. Disk-to-head lubricant transfer leads to lubricant pickup on the slider and also causes depletion of lubricant on the disk. In this paper, we experimentally and numerically investigate the process of disk-to-head lubricant transfer using a half-delubed disk, and we propose a parametric model based on the experimental results. We also investigate the dependence of disk-to-head lubricant transfer on the disk lubricant thickness, lubricant type, and the slider air bearing surface (ABS) design. It is concluded that disk-to-head lubricant transfer occurs without slider-disk contact and there can be more than one timescale associated with the transfer. Furthermore, the transfer increases nonlinearly with increasing disk lubricant thickness. Also, it is seen that the transfer depends on the type of lubricant used and is less for Ztetraol than for Zdol. The slider ABS design also plays an important role, and a few suggestions are made to improve the ABS design for better lubricant performance.

Experimental and Numerical Investigation of Dynamic Instability in the Head Disk Interface at Proximity

2005 ◽  
Vol 127 (3) ◽  
pp. 530-536 ◽  
Author(s):  
Rohit Ambekar ◽  
Vineet Gupta ◽  
David B. Bogy
Keyword(s):  
Dynamic Instability ◽  
Hard Disk Drives ◽  
Areal Density ◽  
Simulation Software ◽  
Flying Height ◽  
Stable Fly ◽  
Lubricant Thickness ◽  
Disk Interface ◽  
The Difference ◽  
Fly Height

As the flying height decreases to achieve greater areal density in hard disk drives, different proximity forces act on the air bearing slider, which results in fly height modulation and instability. Identifying and characterizing these forces has become important for achieving a stable fly height at proximity. One way to study these forces is by examining the fly height hysteresis, which is a result of many constituent phenomena. The difference in the touchdown and takeoff rpm (hysteresis) was monitored for different slider designs, varying the humidity and lubricant thickness of the disks, and the sliders were monitored for lubricant pickup while the disks were examined for lubricant depletion and modulation. Correlation was established between the observed hysteresis and different possible constituent phenomena. One such phenomenon was identified as the Intermolecular Force from the correlation between the lubricant thickness and the touchdown velocity. Simulations using 3D dynamic simulation software explain the experimental trends.

A Method for Characterizing the Head-Disk Interface Dynamics Near the Touchdown Conditions Using the Magnetic Fly-Height

2020 ◽  
Author(s):  
Rahul Rai ◽  
Abhishek Srivastava ◽  
Bernhard Knigge ◽  
Aravind N. Murthy
Keyword(s):  
Hard Disk Drives ◽  
Areal Density ◽  
Disk Surface ◽  
Disk Drives ◽  
Head Disk Interface ◽  
Soft Contact ◽  
Disk Interface ◽  
Magnetic Spacing ◽  
Bearing Stiffness ◽  
Fly Height

Abstract Recent growth in the cloud storage industry has created a massive demand for higher capacity hard disk drives (HDD). A sub-nanometer head media spacing (HMS) remains the most critical pre-requisite to achieve the areal density needed to deliver the next generation of HDD products. Designing a robust head-disk interface (HDI) with small physical clearance requires the understanding of slider dynamics, especially when the head flies in proximity to the disk surface. In this paper, we describe a method using the magnetic read-back signal to characterize the head fly-height modulations as it undergoes a transition from a free-flying state to soft contact with the disk surface. A technique based on the magnetic fly-height sensitivity is introduced for the identification of the transition plane that corresponds to the onset of the touchdown process. Additionally, the proposed magnetic spacing based meteorology is used to study the effect of the air bearing stiffness on the magnitude of the slider vibrations induced by intermittent head-disk interactions. The information about the minimum spacing while maintaining the stable flying conditions can help in reducing the head-disk interaction risk that can enable a low clearance interface.

scholarly journals The Head-Disk Interface Roadmap to an Areal Density of Tbit/in2

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Bruno Marchon ◽  
Thomas Pitchford ◽  
Yiao-Tee Hsia ◽  
Sunita Gangopadhyay
Keyword(s):  
Hard Disk Drives ◽  
Rotating Disk ◽  
Areal Density ◽  
Disk Surface ◽  
Inert Atmosphere ◽  
Annual Growth Rate ◽  
Head Disk Interface ◽  
Bit Patterned Media ◽  
Disk Interface ◽  
Compound Annual Growth Rate

This paper reviews the state of the head-disk interface (HDI) technology, and more particularly the head-medium spacing (HMS), for today’s and future hard-disk drives. Current storage areal density on a disk surface is fast approaching the one terabit per square inch mark, although the compound annual growth rate has reduced considerably from ~100%/annum in the late 1990s to 20–30% today. This rate is now lower than the historical, Moore’s law equivalent of ~40%/annum. A necessary enabler to a high areal density is the HMS, or the distance from the bottom of the read sensor on the flying head to the top of the magnetic medium on the rotating disk. This paper describes the various components of the HMS and various scenarios and challenges on how to achieve a goal of 4.0–4.5 nm for the 4 Tbit/in2density point. Special considerations will also be given to the implication of disruptive technologies such as sealing the drive in an inert atmosphere and novel recording schemes such as bit patterned media and heat assisted magnetic recording.

Experimental and Numerical Investigation of Dynamic Instability in the Head Disk Interface at Proximity

2004 ◽  
Author(s):  
Rohit Ambekar ◽  
Vineet Gupta ◽  
David B. Bogy
Keyword(s):  
Dynamic Instability ◽  
Hard Disk Drives ◽  
Areal Density ◽  
Simulation Software ◽  
Flying Height ◽  
Stable Fly ◽  
Lubricant Thickness ◽  
Disk Interface ◽  
The Difference ◽  
Fly Height

As the flying height decreases to achieve greater areal density in hard disk drives, different proximity forces act on the air bearing slider, which results in fly height modulation and instability. Identifying and characterizing these forces has become important for achieving a stable fly height at proximity. One way to study these forces is by examining the fly height hysteresis, which is a result of many constituent phenomena. The difference in the touchdown and takeoff rpm (hysteresis) was monitored for different slider designs, varying the humidity and lubricant thickness of the disks, and the sliders were monitored for lubricant pickup while the disks were examined for lubricant depletion and modulation. Correlation was established between the observed hysteresis and different possible constituent phenomena. One such phenomenon was identified as the Intermolecular Force from the correlation between the lubricant thickness and the touchdown velocity. Simulations using 3D dynamic simulation software explain the experimental trends.

Smear Growth of Siloxane Outgas at Laser Heating

2017 ◽  
Author(s):  
Hiroshi Tani ◽  
Norio Tagawa ◽  
Renguo Lu ◽  
Shinji Koganezawa
Keyword(s):  
Laser Heating ◽  
Thermal Evaporation ◽  
Laser Light ◽  
Hard Disk Drives ◽  
Areal Density ◽  
Disk Surface ◽  
Disk Drives ◽  
Flash Temperature ◽  
Magnetic Head ◽  
Magnetic Disk

Siloxane outgas is well known to cause smears on magnetic head sliders. Siloxane outgas is vaporized from certain components in hard disk drives (HDDs), that adsorbs on the magnetic disk surfaces, and SiO2 that is denatured from siloxane by flash temperature at a slider and disk contact gets accumulated on the slider surface. On the other hand, heat assisted magnetic recording (HAMR) is being developed to improve areal density. In HAMR, a laser light heats the magnetic disk surface to 400–500 K. Siloxane adsorbed on a disk surface easily gets desorbed from the disk surface owing to thermal evaporation and dissociation by laser heating. In this study, we have studied smear growth from siloxane outgas on laser heating. We observe that the siloxane adsorbed on the disk surface grew on the glass surface above the disk surface at the laser heating spot.

Experimental Investigation of the Effect of Hydrocarbon Oil Contamination on a Disk Surface

2016 ◽  
Author(s):  
Young Woo Seo ◽  
Andrey Ovcharenko ◽  
Yongqi Yan ◽  
Frank E. Talke
Keyword(s):  
Hard Disk Drives ◽  
Disk Surface ◽  
Spindle Motor ◽  
Gas Chromatography Mass Spectrometry ◽  
Oil Contamination ◽  
Disk Interface ◽  
Force Microscopy ◽  
Angle Measurements ◽  
Atomic Force ◽  
Hydrocarbon Oil

Hydrocarbon oil is used to lubricate the spindle motor as well as the pivot actuator arm in current hard disk drives. Previous investigations using molecular dynamics have shown that hydrocarbon oil can contaminate the head-disk interface. In this paper, an experimental study is conducted to investigate the mechanism of hydrocarbon oil contamination on the disk surface using contact angle measurements, atomic force microscopy (AFM), ellipsometry, and gas chromatography mass spectrometry (GC-MS).

Correlation of Disk Topography Waves With Nanometer Scale Lubricant Moguls

2017 ◽  
Author(s):  
Andrey Ovcharenko ◽  
Tom Karis ◽  
Jih-Ping Peng
Keyword(s):  
Shear Stress ◽  
Surface Topography ◽  
Areal Density ◽  
Disk Surface ◽  
Peak Height ◽  
Lubricant Thickness ◽  
Height Control ◽  
Magnetic Performance ◽  
Carbon Overcoats ◽  
Fly Height

Magnetic recording disk carbon overcoats are lubricated with nanometer thick films of perfluoropolyether lubricant. It is well-known that lubricant thickness redistribution takes place due to air shear stress oscillation at air bearing resonant frequencies and also due to shear stress oscillation induced by disk topography waves on test tracks. We extended this work to demonstrate correlation between surface topography and lubricant redistribution on whole disk surfaces. Lubricant moguls are shown to form over regions of the disk surface which have topography waves that are half the slider length, and the lubricant thickness peak is out of phase down track from the topography peak height. There is a critical relative humidity above 20% beyond which moguls are readily formed by the slider flying at 10 nm without thermal fly height control. The significance of the lubricant redistribution for drive magnetic performance has long been the subject of debate. These results demonstrate that lubricant thickness redistribution on the order of atomic diameters can degrade magnetic performance, and that the surface topography waves alone can degrade areal density by as much as 2%.

Atomic Force Microscopy of Magnetic Rigid Disks and Sliders and Its Applications to Tribology

1991 ◽  
Vol 113 (3) ◽  
pp. 452-457 ◽  
Author(s):  
Bharat Bhushan ◽  
G. S. Blackman
Keyword(s):  
Disk Surface ◽  
Lateral Resolution ◽  
Measurement Tool ◽  
Lubricant Thickness ◽  
Strong Function ◽  
Force Microscopy ◽  
Real Area Of Contact ◽  
Atomic Force ◽  
Rigid Disks ◽  
Real Area

Surface topography measurements of magnetic rigid disks and a slider are made using an atomic force microscope (AFM) and a conventional noncontact optical profiler (NOP). The lateral resolution for the surface topographs spans the range of 1 μm down to 2 nm. Topography measurements are used to predict summit statistics and the real area of contact statistics. We find that contact statistics predictions are a strong function of the lateral resolution of the roughness measurement tool. As the magnetic slider comes into contact with the disk surface, the nanoasperities (detected by AFM) plastically deform instantly and subsequently the load is supported by the elastic deformation of microasperities (detected by NOP). AFM also allows the measurements of lubricant-thickness distributions on smooth surfaces. Examples for magnetic disks are presented.

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