Flying Stiction, Lubricant Pick-Up and Carbon-Overcoat Wear of Magnetic Heads

1999 ◽  
Vol 121 (1) ◽  
pp. 97-101 ◽  
Author(s):  
Chao Gao ◽  
Peihua Dai ◽  
Vinh Vu
Keyword(s):  
Fold Increase ◽  
Static Friction ◽  
Disk Surface ◽  
Exponential Dependence ◽  
Magnetic Head ◽  
Bearing Surface ◽  
Lubricant Thickness ◽  
Carbon Overcoat ◽  
Carbon Coated ◽  
Secondary Ion

Flying stiction, a high static friction force resulting from a magnetic head seeking/flying over a disk surface, has posed a new challenge in magnetic-disk tribology for low flying heights (˜30 nm or less), as demanded by high recording densities. Two types of magnetic heads were used in this study. A more than 10-fold increase in flying stiction force was observed for the carbon coated heads after a 24 hours of seeking/flying over the disk surface. Using Time of Flight Secondary Ion Mass Spectroscopy and a scanning micro-ellipsometer, we found that the lubricant pickup during seeking/flying operation was responsible for the observed 10-fold increase of the flying stiction force. A nearly exponential dependence of flying stiction force on lubricant amount picked up on the air bearing surface (ABS) of the magnetic heads was found. For 24 hours of seeking/flying time, the lubricant accumulated on the ABS surfaces can be up to 1.5 nm, comparable to the lubricant thickness on the disk surfaces. The lubricant amount was found quite uniformly distributed over the ABS surface of the head. Wear on the carbon overcoat of the magnetic heads was also measured, and was equivalent to approximately 1 nm carbon loss for a 24-hour seeking/flying period. The wear rate of the carbon overcoat was very fast for short periods of seeking time (˜2 hours) and slowed down to near-zero as lubricant built up on the ABS surface, indicating that the lubricant on the head protected carbon wear. The wear of carbon overcoat strongly suggests that intermittent physical contacts between the disk surface and head ABS occurred during seeking/flying operations.

Wear Characteristics of Carbon-Coated Magnetic Rigid Disks With Well-Defined Surface Texture

1993 ◽  
Vol 115 (4) ◽  
pp. 573-577 ◽  
Author(s):  
Hideaki Tanaka ◽  
Katsuhiko Shiota ◽  
Kenichi Gomi ◽  
Yoshihiko Miyake
Keyword(s):  
Surface Texture ◽  
Disk Surface ◽  
Wear Depth ◽  
Carbon Overcoat ◽  
Surface Textures ◽  
Wear Characteristics ◽  
Apparent Area ◽  
Rigid Disks ◽  
Carbon Coated ◽  
Lithography Technique

Wear characteristics are described for carbon-coated magnetic rigid disks with well-defined surface textures. Concentric circular hills with uniform height (ca. 80 nm) are produced on a disk surface using a photo-lithography technique, to control the apparent area of contact with a slider. Wear depth on the order of nanometers of the carbon overcoat is evaluated from the decrease in hill height after a drag test. Wear depth increases proportionally with the increase in average contact pressure, which is calculated from the load and apparent area of contact between the disk and slider. Lubricant diminishes wear of the carbon overcoat approximately 50 percent compared with that of an unlubricated overcoat.

Lubricant Performance in Magnetic Thin Film Disks With Carbon Overcoat—Part II: Durability

1991 ◽  
Vol 113 (1) ◽  
pp. 32-37 ◽  
Author(s):  
J. L. Streator ◽  
B. Bhushan ◽  
D. B. Bogy
Keyword(s):  
Thin Film ◽  
Disk Surface ◽  
Low Friction ◽  
Carbon Overcoat ◽  
Liquid Lubricant ◽  
Carbon Coated ◽  
Friction Measurements ◽  
Lubricant Performance ◽  
Lubricant Viscosity ◽  
Pfpe Lubricants

Several perfluoropolyether (PFPE) lubricants are evaluated in terms of their ability to maintain low friction and resist wear. The lubricants tested include three nonpolar liquid lubricants and one polar liquid lubricant. Dynamic friction measurements are presented for an IBM 3380-type slider in contact with 130 mm carbon-coated thin film disks. Disk surface run-in and disk durability are evaluated by monitoring the friction force during constant speed sliding. Disk run-in is presented as a function of lubricant thickness and sliding speed, while disk durability is determined for different disk topographies and lubricant thicknesses. It was found that lubricant viscosity was well correlated with the amount of disk run-in and the number of sliding cycles until disk failure. It is proposed that the greater wear durability of the less viscous lubricants can be attributed to their greater mobility on the disk surface.

Improvement of the Static and Dynamic Characteristics of Magnetic Head Sliders by Optimum Design

1999 ◽  
Vol 122 (1) ◽  
pp. 280-287 ◽  
Author(s):  
Hiromu Hashimoto ◽  
Yasuhisa Hattori
Keyword(s):  
Objective Function ◽  
Optimum Design ◽  
Amplitude Ratio ◽  
Optimization Technique ◽  
Hard Disk Drives ◽  
Maximum Amplitude ◽  
Disk Surface ◽  
Operating Conditions ◽  
Magnetic Head ◽  
Design Variables

The aim of this paper is to develop a general methodology for the optimum design of magnetic head sliders in improving the spacing characteristics between a slider and disk surface under static and dynamic operating conditions of hard disk drives and to present an application of the methodology to the IBM 3380-type slider design. To generate the optimal design variables, the objective function is defined as the weighted sum of the minimum spacing, the maximum difference in the spacing due to variation of the radial location of the head, and the maximum amplitude ratio of the slider motion. Slider rail width, taper length, taper angle, suspension position, and preload are selected as the design variables. Before the optimization of the head, the effects of these five design variables on the objective function are examined by a parametric study, and then the optimum design variables are determined by applying the hybrid optimization technique, combining the direct search method and successive quadratic programming. From the obtained results, the effectiveness of optimum design on the spacing characteristics of magnetic heads is clarified. [S0742-4787(00)03701-2]

Time-Frequency Analysis of Slider Dynamics and the Effect of Lubricant

2002 ◽  
Author(s):  
Saurabh K. Deoras ◽  
Frank E. Talke
Keyword(s):  
Frequency Analysis ◽  
Disk Surface ◽  
Air Bearing ◽  
Lubricant Film Thickness ◽  
Lubricant Thickness ◽  
Laser Doppler Vibrometry ◽  
Time Frequency Analysis ◽  
Time Frequency ◽  
Pitch Frequency ◽  
Transient Events

The dynamics of pico sliders is investigated during scratch impact using laser Doppler vibrometry. Airbearing frequencies and damping of the pitch frequency are studied as a function of disk velocity for lubricant thickness values of 1.6nm, 1.0nm and 2.0nm. In addition, time-frequency analysis is used to study transient events during slider-scratch impact. The results indicate that the slider dynamics is not only a function of the design of the air-bearing, but also of the velocity and the characteristics of the lubricant film thickness on the disk surface.

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.

Study of Tribochemical Processes on Hard Disks Using Photoemission Electron Microscopy

1999 ◽  
Vol 121 (4) ◽  
pp. 961-967 ◽  
Author(s):  
Simone Anders ◽  
Thomas Stammler ◽  
Walton Fong ◽  
Chao-Yuan Chen ◽  
David B. Bogy ◽  
...  
Keyword(s):  
Hard Disks ◽  
Chemical Modifications ◽  
Hard Carbon ◽  
Carbon Overcoat ◽  
Chemical Changes ◽  
X Ray ◽  
Tribochemical Processes ◽  
Carbon Coated ◽  
Photoemission Electron ◽  
Wear Tests

The interface between hard disk and slider involves mechanical and tribochemical processes between the hard carbon overcoat of the disk, the lubricant, and the carbon coated or uncoated slider surface. These processes have been studied by two related X-ray techniques—Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy and Photoemission Electron Microscopy (PEEM) using X-rays. NEXAFS allows studying the elemented composition and chemical bonding in a material, whereas PEEM combines this ability with imaging of the sample. Lubricated and unlubricated disks were worn under various conditions using carbon coated and uncoated sliders. The wear tracks on the hard disks were investigated using PEEM to find chemical and elemental changes caused by the wear. Local NEXAFS spectra taken in wear tracks using the PEEM microscope show no chemical changes on unlubricated disks, just a reduction of the hard carbon overcoat thickness. On lubricated disks remarkable chemical modifications of the lubricants caused by the wear are observed if the disks failed the wear tests. The chemical changes are manifested in a formation of various new carbon-oxygen (mostly carboxylic) bonds in the wear tracks and in a strong reduction of the amount of fluorine and carbon. The chemical modifications were only found inside the wear tracks and are clearly caused by the wear. It was found that lubricant degradation is not solely a mechanical process of molecule scission but accompanied by oxidation reactions. The chemical changes were strongly correlated to the tribological behavior of the disks: the worse the disks performed in the wear tests, the stronger were the chemical modifications.

Experimental Study of Long-Term Static Friction and Magnetic Slider/Disk Interplanar Separation

1996 ◽  
Vol 118 (1) ◽  
pp. 12-20 ◽  
Author(s):  
C. T. Gerber ◽  
B. Bhushan ◽  
N. V. Gitis
Keyword(s):  
Experimental Study ◽  
Parallel Plate ◽  
Static Friction ◽  
Lubricant Thickness

Capacitance between a slider and disk was measured to relate slider/disk interplanar separation to static friction. The parallel plate capacitance formula was used to convert the capacitance into separation with a resolution of less than 1 nm. Separation and coefficient of static friction (stiction) were measured using assorted lubricant thicknesses with and without bonding on polished and textured disks. Separation was measured during contact start/stop (CSS) and long term slider dwell times, after which static friction was measured. Polished disks had high stiction events with smaller separations during and after the stiction event, unlike textured disks. Long-term dwell studies showed the coefficient of static friction and slider micro descent (decrease in interplanar separation) to be greatest with greater lubricant thickness and polished disks. Static friction and separation with bonded and unlubricated disks were time independent.

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