A model for lubricant flow dynamics under a scanning laser beam has been constructed for a heat-assisted magnetic recording system. The effects of evaporation, thermocapillary stress and thermoviscosity on the lubricant depletion on both glass and aluminium disks are systematically studied. Our results indicate that both evaporation and thermocapillary stress are able to deplete non-negligible amount of Z-type PFPE lubricants with a low molecular weight from the disk surface within nanoseconds. Evaporation is the dominant lubricant removal mechanism when low molecular weight lubricant is used. Evaporation is significantly reduced when high molecular weight PFPE lubricants are used. Our simulations show that the performance of head/disk interface of heat-assisted magnetic recording systems may be significantly deteriorated when lubricants with improper properties are used.

http://iopscience.iop.org/article/10.1088/0957-4484/18/21/215702/pdf

Modelling and simulation of the lubricant depletion process induced by laser heating in heat-assisted magnetic recording system

A model is presented that calculates the equilibrium lubricant thickness on a slider, resulting from a steady state where net inflow from disk evaporation equals net outflow from evaporation back to the disk, and flow to the slider back end from air shear. Based on experimental vapor pressure and viscosity data, and using surface viscosity enhancement factor and disjoining pressure values available in the literature, this model predicts a transition from a flooded regime for molecular weight M/sub n/ below 1.5 kDaltons to a starved regime where slider lubricant thickness drops to a value close to zero. At the same time, lubricant accumulation to the slider back end is expected to decrease exponentially.

A model for lubricant flow from disk to slider

As areal density in disk drive technology is marching towards the Tbit∕in.2 mark, the slider-to-disk spacing will be required to be within only a few nanometers. Coupled with very high slider velocities (>40m∕s), this leads to extremely high shear stresses on the nanometer-thin lubricant film at the disk surface. As a result, the lubricant film tends to exhibit local redistribution on a micrometer lateral level, decreasing the overall clearance and impacting the integrity of the interface. This paper describes a different approach to functionalized lubricant, where in addition to functional groups placed at the end of the chain, additional attachment moieties are introduced within the main polymer chain. The benefits of this approach is twofold: it increases adhesive interaction with the disk surface, therefore increasing the effective surface viscosity, while at the same time “tying” down the free backbone length for increased clearance. Fabrication, characterization, and performance data obtained on act...

Multidentate functionalized lubricant for ultralow head/disk spacing in a disk drive

A model is presented that accounts for the observation of periodic lubricant ripples formed when a slider is flying on-track over a lubricated disk surface. It is shown that lubricant flow modulation from the air shear stress due to the low flying slider acting as a spring is responsible for the observed corrugation, as repeated flying over the same track enhances the effect. This is somewhat moderated by the relaxation of the lubricant perturbation, by surface diffusion. Depending on the relative magnitude of the shear and diffusion processes, the system can find itself into regions of stability where small perturbations decay away, or regions of instability where they increase exponentially. Instability is enhanced for lower fly height and higher disk rotational frequency, making it a challenge for future growth in disk drive performance and areal density.

Modeling the washboard effect at the head/disk interface

Thermal fly-height control sliders that are capable of subnanometer level actuation are used to investigate the vertical, down-track, and off-track slider dynamics in slider-disk lubricant contact. Slider-lubricant contact introduces significant excitation in all three directions, and the slider dynamics is dependent on the degree of lubricant-contact. The lubricant surface has a significant role in determining the physical clearance and slider fly-height. While slider-lubricant contact may be successfully achieved by carefully controlling the heater power, improved slider designs and associated heater induced protrusion profiles are necessary to successfully mitigate contact induced vibrations and meet the challenges for future hard disk drives.

Slider Dynamics in the Lubricant-Contact Regime

A simple method is introduced to contaminate either the slider or the disk with a small amount of lubricant, with the intent of studying the interaction between the slider and the lubricant layer on hard disks at low mechanical fly heights. Lubricant ripples at a frequency of 220-280 kHz, corresponding to the second pitch mode of the sliders used, were observed on the disk with an optical surface analyzer. Using laser Doppler velocimetry, a corresponding fly height modulation of up to 20 nm was measured on the slider body. It is hypothesized that this is due to a sustained stick-slip mechanism involving lubricant bridging.

Experimental study of lubricant-slider interactions

Presents studies on lubricant mogul formation when a slider flies over a disk surface. In the range of parameters used in this study, moguls form and reach a steady-state pattern within 100 revolutions. During this period, no significant net lubricant loss is observed in the track. The completion of the full mogul pattern is followed by an asymptotic lubricant loss from the track. The loss was not compensated by an increase in thickness outside the track. It is speculated that this lubricant loss from the disk is initiated when the peak thickness of the moguls exceeds the critical dewetting thickness, therefore allowing an energetically favored process. Theoretical modeling based on Van der Waal's interactions is presented.

Genesis and evolution of lubricant moguls

This paper presents a novel method for studying the relaxation characteristics of a molecularly thin lubricant film. The thickness dependent diffusion constant is measured by monitoring the temporal decay of a lubricant film thickness with a well-controlled initial sinusoidal thickness modulation. The lubricant film thickness can also be modulated by flying a slider in seek mode, creating a 2D "mogul" pattern. Using the previously measured diffusion coefficients, the relaxation of these moguls is simulated and compared with the experimental relaxation images obtained with an Optical Surface Analyzer.

Direct measurement of lubricant relaxation on a disk surface

This paper reviews the present state of understanding of lubricant-slider interactions in a rigid disk drive. As slider flying heights are rapidly approaching the intrinsic limit of a disk topography (1-3 nm), it has become apparent that disk-slider clearance of less than a nanometer can be achieved, at least on a laboratory set-up. We will discuss the implication of such low spacing on the lubricant film behavior, and provide general physical arguments that attempt to highlight lubricant attributes that are relevant under those clearance conditions

Lubricant Dynamics in the Sub-Nanometer Clearance Regime

Handle everyday research tasks with reliable, citation-backed results

Your personal Research Agent to handle research tasks with citation-backed results

Popular Tasks used by Researchers

How can I help with your research?

Meet SciSpace

Get more enhanced response by uploading the PDFs you want me to reference.

No relevant PDFs in your library

SciSpace is the AI research assistant for academics. Run systematic literature reviews on 280M+ papers, and write papers with cited sources. Trusted by 1M+ students, PhDs & researchers.

SciSpace | AI for Research

Analyze PDFs

Code & Manuscripts

Funding & Grants

Literature & Patents

Medical & Clinical Data

Systematic Review

Visualize & Present

Web & Data

Build a Google Scholar-like website for your research.

Build a website

Create charts and images for your research

Create a Chart

Write a paper for submission to a journal

Draft a manuscript

Patent Search

Design eye-catching scientific posters in minutes.

Scientific Poster Generation

Systematic Literature Review

One task is running at the moment. Your messages will be shown right after.

Drag and drop or click here to browse

Loved by <highlight>1 million+</highlight> researchers

Extract a list of specific topics and their sources from unstructured text

Topics

Compare and analyze relevant papers that matches with your search

Papers

Get insights from PDFs and bookmarked papers from your library

My library

Recent searches

Try searching for:

Catch AI-generated content in scholarly and non-scholarly content

{ai} Detector

Ai Writer

Get PDF Summaries, highlighted text explanations 

Chat with PDF

Effortlessly create in-text citations and bibliographies in APA and 2,500 other formats

Citation generator

Get explanations, summaries, and answers on academic papers

Ease up your research workflow with {scispace}'s cohort of exciting AI tools

Elevate your academic writing skills and convey your ideas the way you want

Paraphraser

Explore our range of reading and writing tools

Your file is being prepared and should be ready in a few minutes. If it's a large file, it might take a bit longer. You can close this window, and we'll email you the file when it's done.

You have reached a maximum limit of <strong>{limit}</strong> columns in the table. Remove at least <strong>1</strong> column to add or create another one.

R. Pit

Author Tools

Chat about Author