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.

Transient Thermal Response of the Media by Free Space Laser Heating in Heat Assisted Magnetic Recording

2016 ◽  
Author(s):  
Shaomin Xiong ◽  
Robert Smith ◽  
Na Wang ◽  
Dongbo Li ◽  
Erhard Schreck ◽  
...  
Keyword(s):  
Magnetic Recording ◽  
Heat Conduction Problem ◽  
Temperature Response ◽  
Thermal Response ◽  
Areal Density ◽  
Heat Assisted Magnetic Recording ◽  
Lumped Model ◽  
The Media ◽  
Transient Thermal ◽  
Transient Thermal Response

Heat assisted magnetic recording (HAMR) promises to deliver higher storage areal density than the current perpendicular magnetic recording (PMR) product. A laser is introduced to the HAMR system to heat the high coercively magnetic media above the Curie temperature (Tc) which is as high as 750 K in order to enable magnetic writing. The thermal response of the media becomes very critical for the success of the data writing process. In this paper, a new method is proposed to understand the transient thermal behavior of the HAMR media. The temperature response of the media is measured based on thermal erasure of the magnetically written signal. A lumped model is built to simplify the heat conduction problem to understand the transient thermal response. Finite element modeling (FEM) is implemented to simulate the transient thermal response of the media due to the laser pulse heating. The experimental and simulation results show fairly good agreement.

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.

Experimental Study on Laser-Induced Protrusion in Heat-Assisted Magnetic Recording

2020 ◽  
Author(s):  
Qilong Cheng ◽  
Haoyu Wang ◽  
Siddhesh V. Sakhalkar ◽  
David B. Bogy
Keyword(s):  
Magnetic Recording ◽  
Laser Heating ◽  
Hot Spot ◽  
Magnetic Layer ◽  
Optical Power ◽  
Linear Velocity ◽  
Component Level ◽  
Heat Assisted Magnetic Recording ◽  
Power Change ◽  
The Media

Abstract In heat-assisted magnetic recording (HAMR), a laser is introduced to create a hot spot on the media and locally heat the magnetic layer to its Curie temperature. Besides the optical power that the laser provides to the media, thermal energy diffuses inside the slider and induces an extra protrusion, which is called laser-induced protrusion (LIP). The LIP needs to be considered and compensated during flying in the HAMR conditions. In this study, we focus on long timescale (milliseconds) of laser heating during the flying condition. When the laser is switched from OFF to ON, the touchdown power, indicated by an acoustic emission (AE) sensor, decreases due to spacing loss and the touchdown power change (ΔTDP) is used as the measure of the LIP. A component-level spinstand stage for HAMR heads and media is used to study the LIP as a function of laser-on time, laser current and linear velocity. Our experimental results show that it takes around 20 ms for the LIP to reach steady state and the protrusion size is proportional to the square of laser current. As the operating linear velocity increases from 12 m/s to 24 m/s, the LIP decreases by approximately 52%.

A Numerical Investigation of the Nanoscale Heat Transfer in Heat Assisted Magnetic Recording

2017 ◽  
Author(s):  
Yueqiang Hu ◽  
Haoyu Wu ◽  
Yonggang Meng ◽  
David Bogy
Keyword(s):  
Heat Transfer ◽  
Magnetic Recording ◽  
Near Field ◽  
Field Analysis ◽  
Management Problem ◽  
Heat Management ◽  
Heat Assisted Magnetic Recording ◽  
The Media ◽  
Em Field

The heat management problem in the heat assisted magnetic recording (HAMR) has been a long-term issue. In this paper, we investigated the temperature increase of a “lollipop” type near field transducer (NFT) in HAMR. We included the electromagnetic (EM) field analysis in the modeling and considered the back-heating from the media to the head with various heat transfer mechanisms. The results showed that the overcoat layer of the NFT plays an important role for protecting the NFT from high temperature. Degradation of the overcoat layer may result in the early failure of the NFT.

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.

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