scholarly journals Slider Posture Effects on Air Bearing in a Heat-Assisted Magnetic Recording System

2012 ◽  
Vol 2012 ◽  
pp. 1-6 ◽  
Author(s):  
Kyaw Sett Myo ◽  
Weidong Zhou ◽  
Xiaoyang Huang ◽  
Shengkai Yu ◽  
Wei Hua
Keyword(s):  
Magnetic Recording ◽  
Pitch Angle ◽  
Direct Simulation Monte Carlo ◽  
Spot Size ◽  
Air Bearing ◽  
Slider Bearing ◽  
Noticeable Effect ◽  
Heat Assisted Magnetic Recording ◽  
Temperature Changes ◽  
Bearing Force

This paper reports the effects of slider posture on the slider bearing in a heat-assisted magnetic recording (HAMR) system with the direct simulation Monte Carlo (DSMC) method. In this HAMR system, the heat issues on the slider bearings are assumed to be caused by a heated spot on the disk and/or slider body itself at various pitch angles. The simulation results show that with a heated spot on the disk, the air bearing pressure and air bearing force that acted on the slider surface will increase when the pitch angle becomes larger. It is also found that the bearing force increases with the heated spot size and the effects of a heated spot become more obvious at a larger pitch angle. On the other hand, the slider body temperature is observed to have a noticeable effect on air bearing pressure and force. The smaller pitch angle enlarges the tendency of bearing force variations with the slider temperature and makes the slider more sensitive to its temperature changes.

scholarly journals Novel droplet near-field transducer for heat-assisted magnetic recording

Nanophotonics ◽  
2015 ◽  
Vol 4 (4) ◽  
pp. 503-510 ◽  
Author(s):  
Jacek Gosciniak ◽  
Marcus Mooney ◽  
Mark Gubbins ◽  
Brian Corbett
Keyword(s):  
Surface Plasmon ◽  
Magnetic Recording ◽  
Near Field ◽  
Metal Structure ◽  
Spot Size ◽  
Impedance Match ◽  
Localized Surface Plasmon ◽  
Heat Assisted Magnetic Recording ◽  
Localized Surface Plasmon Resonances ◽  
High Degree

AbstractTwo main ingredients of plasmonics are surface plasmon polaritons (SPP) and localized surface plasmon resonances (LSPR) as they provide a high degree of concentration of electromagnetic fields in the vicinity of metal surfaces, which is well beyond that allowed by the diffraction limit of optics. Those properties have been used in the new technique of heat assisted magnetic recording (HAMR) to overcome an existing limit of conventional magnetic recording by utilizing a near-field transducer (NFT). The NFT designs are based on excitation of surface plasmons on a metal structure, which re-radiate with a subdiffraction limited light spot confined in the near field. In this paper, we propose a novel “droplet”-shaped NFT, which takes full advantage of a recenltly proposed Mach–Zehnder Interferometer (MZI), a coupling arrangement that allows optimal coupling of light to the transducer. The droplet design ensures better impedance match with the recording media and, consequently, better coupling of power. The droplet design results in very high enhancement of the electric field and allows the confinement of light in a spot size much smaller than the present stateof- the-art lollipop transducer.

Air Bearing Pushback in Heat Assisted Magnetic Recording

2019 ◽  
Author(s):  
Shaomin Xiong ◽  
Robert Smith ◽  
Chanh Nguyen ◽  
Youfeng Zhang ◽  
Yeoungchin Yoon
Keyword(s):  
Magnetic Recording ◽  
Hard Disk Drives ◽  
Hard Disk ◽  
Disk Drive ◽  
Flying Height ◽  
Air Bearing ◽  
Magnetic Media ◽  
Heat Assisted Magnetic Recording ◽  
Height Control ◽  
Different Dimensions

Abstract The air bearing surface is critical to the spacing control in current hard disk drives (HDDs). Thermal protrusions, including thermal flying height control (TFC) and writer coil protrusion, drive the reader/writer elements closer to the magnetic media. The spacing control actuation efficiency depends on the air bearing push back response after the TFC or writer protrudes. In the next generation hard disk drive technology, heat assisted magnetic recording (HAMR), laser induced protrusions further complicate the spacing control. The laser induced protrusions, such as the localized NFT protrusion and a wider change of the crown and camber, have very different dimensions and transient characteristics than the traditional TFC and writer protrusion. The dimension of the NFT protrusion is relatively smaller, and the transient is much faster than the TFC protrusion. However, it is found that the NFT protrusion is large enough to generate an air bearing push back effect, which changes the read and write spacing when the laser is powered on. To accurately control spacing in HAMR, this push back effect has to be taken into account.

Effects of Varied Physical Mechanisms on the Evolution of Lubricant Interface During Heat-Assisted Magnetic Recording

2013 ◽  
Author(s):  
Ajaykumar Rajasekharan
Keyword(s):  
Magnetic Recording ◽  
Air Bearing ◽  
Complex Interplay ◽  
Heat Assisted Magnetic Recording ◽  
Physical Mechanisms ◽  
Capillary Stress ◽  
Vapor Recoil ◽  
The Media ◽  
Physical Effects ◽  
Pfpe Lubricants

A concoction of various forces and physical effects (both mechanical and chemical) come into play in the depletion and evolution of the lubricant on the media during a heat-assisted magnetic recording (HAMR) process. They include the air-bearing shear and pressure, capillary pressure, thermo-capillary stress, disjoining pressure, lubricant desorption and the vapor recoil mechanism. The effects of these mechanisms and their complex interplay to stabilize/destabilize the lubricant interface is studied here numerically. Results for Z-type perfluropolyether (PFPE) lubricants with different polydispersity indices (PDI) are summarized.

Effect of Functional End-Groups on the Lubricant Recovery After Heat-Assisted Magnetic Recording (HAMR) Writing

2016 ◽  
Author(s):  
Soroush Sarabi ◽  
David B. Bogy
Keyword(s):  
Magnetic Recording ◽  
Recovery Process ◽  
Spot Size ◽  
Disjoining Pressure ◽  
Pressure Derivative ◽  
Polymer Backbone ◽  
Heat Assisted Magnetic Recording ◽  
Lubricant Depletion ◽  
End Groups ◽  
Short Time

In the developing heat-assisted magnetic recording (HAMR) technology, a laser heats up the magnetic media to the Curie temperature of a few hundred degrees Celsius for a short time of the order of a few nanoseconds. Accordingly, the thin-film lubricant coating on the disk experiences effects such as thermo-capillary shear stress, evaporation, viscosity drop, and eventually, lubricant depletion [1, 2]. Our previous work [3] studied these effects on the lubricant depletion for various lubricants and a prescribed Gaussian temperature distribution with a peak temperature of 350°C and a Full-Width Half Maximum (FWHM) of Ls = 20nm, close to the target laser spot size for HAMR. In order to maintain a reliable head-disk interaction, the lubricant needs to recover to the initial uniform profile. A previous work by Dahl and Bogy [4] studied the recovery process after HAMR writing for Z-dol 2000 using lubrication theory. In this paper, we focus on the effect of the lubricant functional end-groups on the recovery process, using the same method. Z-dol, Z-tetraol, and ZTMD lubricant families have the same polymer backbone but different numbers of hydroxyl end-groups [5]. This difference modifies two key parameters, both affecting the recovery time significantly. First, it changes the bonding ratio and the disjoining pressure properties of the lubricant. Figure 1 shows the disjoining pressure derivative, including both the polar and dispersive components, as a function of film thickness for Z-dol2000, Z-tetraol2200, and ZTMD2200 based on experiments [1, 6, 7]. Second, a major increase in lubricant viscosity occurs as the number of hydroxyl end-groups increases from two (Z-dol) to four (Z-tetraol) to eight (ZTMD) [3]. Fig. 2 shows the viscosity μ(h) as a function of the local lubricant thickness for all three different families of lubricants at the room temperature.

Viscoelastic Effects on Lubricant Depletion and Recovery Under Heat-Assisted Magnetic Recording (HAMR) Conditions

2016 ◽  
Author(s):  
Soroush Sarabi ◽  
David B. Bogy
Keyword(s):  
Relaxation Time ◽  
Magnetic Recording ◽  
Viscoelastic Behavior ◽  
Spot Size ◽  
Deborah Number ◽  
Lubrication Theory ◽  
Laser Spot ◽  
Laser Spot Size ◽  
Heat Assisted Magnetic Recording ◽  
Maxwell Relaxation Time

Heat Assisted Magnetic Recording (HAMR) is a developing data-storage technology in which a laser delivery system is integrated to the conventional HDD air bearing slider that carries the read and write transducers. The laser beam heats a small spot of around 20nm size on the storage media up to few hundred degrees Celsius [1]. This heating causes several effects on the lubricant such as temperature gradient, thermocapillary shear stress, viscosity drop, and evaporation followed by its depletion. Conventionally [2–8], the disk lubricant is considered as a Newtonian viscous fluid that can be fully described by a viscosity parameter μ. However, in rapid heating and forcing conditions like HAMR, the time dependent nature of the lubricant becomes very important. Measurements [9] show that under some conditions the lubricant behaves like a Maxwell viscoelastic fluid that can be described by two parameters: viscosity μ and Maxwell relaxation time λ. Itoh et al. [10] show that the viscoelastic behavior becomes even more considerable in the case of sub-10nm material confinement. Both the Maxwell relaxation time and viscosity can be functions of temperature and lubricant thickness in case of ultra-thin film lubrication. Karis [9] measured Maxwell relaxation time as a function of temperature for a variety of lubricants, such as Z-dol and Z-tetraol. Fig. 1 shows the results of these measurements for both Z-dol and Z-tetraol. Maxwell relaxation time plays a vital role in determining the behavior of the material under thermal and mechanical loads. In order to have a proper understanding of the effect of Maxwell relaxation time, we non-dimensionalize this parameter by the timescale of the problem to introduce a non-dimensional Deborah number De = λU/L. So, De is a function of HAMR temperature T, disk speed U, laser spot size L, and lubricant type. For purely-viscous materials both the Maxwell relaxation time and De are zero and for purely-elastic materials, both are infinity. So in the case of viscoelasticity, if De ≪ 1 the viscosity mode is dominant, if De ≫ 1 the elasticity is dominant, and if De ≈ 1 the material behaves viscoelastically. Therefore, De is good measure for the viscoelastic behavior of the material. Some attempts have been made to fit the lubrication theory for viscoelastic materials using perturbation methods. However these methods require that the Deborah Number be small enough [11]. Fig. 2 shows the Deborah Number as a function of laser spot size for different lubricant temperatures. Accordingly, at the target of a HAMR laser spot size of L = 20nm, the Deborah number is very large and therefore, the material behaves less viscous and more elastic. Therefore, the traditional methods of lubrication theory cannot describe the lubricant’s behavior in this limit. Consequently, we developed anew direct Finite Element Method (FEM) approach to simulate the behavior of the linear viscoelastic Maxwell fluid lubricants under HAMR conditions.

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