Thin film gas lubrication characteristics of flying head slider bearings over patterned media in hard disk drives

2003 ◽  
Vol 9 (5) ◽  
pp. 362-368 ◽  
Author(s):  
N. Tagawa ◽  
A. Mori
2002 ◽  
Vol 124 (3) ◽  
pp. 568-574 ◽  
Author(s):  
Norio Tagawa ◽  
David B. Bogy

This paper describes the air film dynamics for micro-textured flying head slider bearings in magnetic hard disk drives and it discusses their ability to increase the air film damping. In order to study the effects of micro-textures on air film dynamic characteristics of flying head slider bearings, two-dimensional micro-textures are modeled as deterministic rectangular models in the transverse and longitudinal directions. Dynamic analysis of these micro-textured flying head slider bearings is carried out by computing the impulse responses of the sliders and applying the modal analysis method to obtain their modal frequencies, damping ratios, and mode shapes. It is found that micro-textures on air bearing surfaces in the transverse direction have very significant effects and increase the air film damping of the slider’s three vibration modes but do not affect the air film stiffness. The same is not true for micro-texture in the longitudinal direction. The effects of transverse micro-textures’ spacing and depth on the air film dynamics are also numerically investigated in detail. The optimum values for high air film damping ratios are obtained. It is found that transverse micro-textures having small spacing are not very effective, being equivalent to the surface roughness effect.


2000 ◽  
Vol 123 (1) ◽  
pp. 151-158 ◽  
Author(s):  
Norio Tagawa ◽  
Takefumi Hayashi ◽  
Atsunobu Mori

This paper describes the effects of moving three-dimensional nano-textured or patterned disk surfaces on thin film gas lubrication characteristics for flying head slider bearings in magnetic disk storage. In order to perform the most realistic simulation of slider flying characteristics over the textured disk surfaces, the direct numerical simulation method is used, instead of using various averaging techniques. Therefore, a deterministic description of the texture is adopted in this study. A dynamic analysis of the slider responses can be carried out, by solving the air bearing equation based on the linearized Boltzmann equation with the equations of motion of the slider under the excitation of the moving texture simultaneously. The slider’s dynamic responses to moving spaced bumps disk surfaces, including both the circumferentially and radially ridged disk surfaces, are computed systematically and basic slider dynamics over patterned disk surfaces is investigated. The effects of the texture area ratios (= texture width/texture pitch) in the circumferential and radial directions on the slider spacing dynamic modulations as well as the slider static flying characteristics are also studied. Furthermore, the effects of three kinds of texture patterns on the slider flying characteristics are investigated. Considering those simulation results, the design optimization for the texture pattern that minimizes not only the slider static flying height increase but also spacing dynamic modulations is discussed in order to achieve ultra-high density proximity magnetic recording.


Author(s):  
William W. F. Chong ◽  
Mircea Teodorescu ◽  
Homer Rahnejat

In lubricated contact conjunctions film ruptures close to the exit boundary. This significantly affects the load carrying capacity and can lead to direct surface interactions. Nano-scale films (several molecular diameters of the lubricant) are no exception, a fact that has been observed using ellipsometry studies for ultra-thin film conjunctions representative for high storage capacity hard disk drives. Immediately beyond the film rupture an area of cavitation occurs and the continuity of flow condition is breached. It has been shown that for molecularly smooth surfaces solvation effect becomes dominant. This means that the contact exit is subject to discrete drainage of lubricant and may be devoid of a sufficient lubricant for film reformation to occur. This can be a stumbling block in an increasing quest to increase the data storage density of hard disk drives. Wear can become a problem as well as non-uniformity of free surface film at the inlet meniscus. It has been noted that peaks of lubricant can gather in some places, a phenomenon referred to as lubricant mogul. These localized piles of lubricant can exceed the nominally aimed for lubricant film thickness necessary for a given data storage level. This paper carries out an in-depth prediction of ultra thin film lubricant behavior through the contact. Hydrodynamic as well as near surface effects and intermolecular interactions responsible for the supply, formation, cavitation and reformation of thin films in the slider-disk conjunction have been considered.


Author(s):  
Kenji Yanagisawa ◽  
Youichi Kawakubo ◽  
Masato Yoshino

In Hard Disk Drives, lubricants are very important materials to reduce head and disk wear. Therefore, it is necessary to know the lubricant depletion under flying heads. Lubricant depletion due to flying heads has been studied experimentally. We developed simulation program to calculate numerically the change in lubricant thickness under a flying head on a thin-film magnetic disk from 10nm thick lubricant film. In recent HDDs, the lubricants thickness has become molecularly thin and polar lubricants have been used. In this paper, we took account of thickness-dependent lubricants diffusion and viscosity in our simulations to calculate a 1.2 nm thick polar lubricant film used in recent HDDs. The simulated results considering the thickness-dependent diffusion and viscosity showed that depletion was small in molecularly thin lubricant films. We considered it necessary to include thickness-dependent diffusion and viscosity in lubricant depletion simulation.


1992 ◽  
Vol 28 (5) ◽  
pp. 2124-2126 ◽  
Author(s):  
E. Autino ◽  
J.P. Lazzari ◽  
C. Pisella

Author(s):  
Norio Tagawa ◽  
Ken-ichi Kitamura ◽  
Atsunobu Mori

This paper describes the development of novel PZT thin films for active sliders in hard disk drives. So far, it is common that single-layered thin films are used as micro-actuators for conventional PZT thin films such as sol-gel or sputtered thin films. In this study, however, the novel composite PZT thin films are developed. The feature is that sol-gel PZT thin film is deposited on sputtered PZT thin film fabricated on Pt/Ti bottom electrode. These multilayered composite PZT thin films are found to have the higher (111) preferred orientation as well as better P-E hysteresis loop characteristics than not only sol-gel PZT thin films but also sputtered PZT thin films. Furthermore, the piezoelectric strain constant d31 for the novel PZT thin films is identified to be 189 × 10−12m/V. This value is 2.0 times higher than that for conventional PZT thin films and it is found that the novel PZT thin films have good piezoelectric properties.


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