Disk Protrusion Measurement in a Back-Heating Study for Heat Assisted Magnetic Recording

2020 ◽  
Author(s):  
Shaomin Xiong ◽  
Robert Smith ◽  
Erhard Schreck
Keyword(s):  
Heat Transfer ◽  
Magnetic Recording ◽  
Local Heating ◽  
Hard Disk Drives ◽  
Detection Sensitivity ◽  
Experimental Setup ◽  
Heat Assisted Magnetic Recording ◽  
Management Scheme ◽  
The Media ◽  
Disk Spacing

Abstract Heat assisted magnetic recording (HAMR) is a promising technology for the next generation hard disk drives (HDDs). Understanding the heat transfer at nanoscales and implementing a proper thermal management scheme become very critical as a few heat sources and energy delivery components are compactly integrated in a HAMR drive. Recently, a back-heating experimental setup is used to study heat transfer behavior. It is found that the detection of head disk contact and head disk spacing control become more complicated in this experimental setup because the local heating generates a protrusion on the media surface. In this paper, we demonstrate a method to enhance the contact detection sensitivity significantly by modulating the head disk spacing. It shows that a light contact between the head TFC protrusion and media protrusion can be effectively detected. Thereafter, the media protrusion can be measured and the head disk spacing can be well set.

Head Disk Spacing Effect on Heat Transfer in Heat Assisted Magnetic Recording

2017 ◽  
Author(s):  
Shaomin Xiong ◽  
Erhard Schreck ◽  
Sripathi Canchi
Keyword(s):  
Heat Transfer ◽  
Magnetic Recording ◽  
Spacing Effect ◽  
Disk Drive ◽  
Heat Assisted Magnetic Recording ◽  
Heating Source ◽  
Spacing Effects ◽  
Thermal Sensing ◽  
Transfer Mechanisms ◽  
Disk Spacing

Heat transfer at nanometer scale attracts a lot of interest from both academia and industries. The hard disk drive (HDD) industry cares about the heat transfer between the head and disk, as several heating and thermal sensing elements are integrated into the HDD system. Understanding the heat transfer mechanism and its dependency on spacing becomes very critical for heat assisted magnetic recording (HAMR). In this paper, we propose a new method to study the head disk spacing effects on heat transfer by introducing a small perturbation to the spacing while maintaining the heating source unchanged. The dependency of heat transfer on the nanoscale spacing provides insights to the understanding of heat transfer mechanisms inside the nanoscale gap.

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.

Effect of Humidity on the Nanoscale Heat Transfer at the Head-Media Interface

2019 ◽  
Author(s):  
Qilong Cheng ◽  
Yuan Ma ◽  
David Bogy
Keyword(s):  
Heat Transfer ◽  
Magnetic Recording ◽  
Heat Dissipation ◽  
Hard Disk Drives ◽  
Water Layer ◽  
Rate Of Change ◽  
Nanoscale Heat Transfer ◽  
The Media ◽  
Bearing Design ◽  
The Heat Transfer Coefficient

Abstract In hard disk drives (HDD), the head-media spacing has decreased to less than 10 nm. Across this nanoscale gap, the heat transfer between the head and media may affect the air-bearing design, lubricant transfer and contact issues. Thus, understanding the heat transfer mechanism is very important to magnetic recording, especially for Heat Assisted Magnetic Recording (HAMR). In this paper, the heat transfer between a head and a static media is studied. In particular, the effect of humidity on the nanoscale heat transfer between a head and a static media is studied experimentally. From the transient and steady data of the experiments, it is proposed that the dynamic response of head protrusion is faster than heat dissipation. Also, a layer of water is assumed to form between the head and the media under high humidity. The water-layer affects the spacing and the heat transfer coefficient across the interface. In the near-contact regime, namely when the clearance is less than 2 nm or so, the protrusion interacts with the water-layer on the media, resulting in a lower rate of change of cooling.

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.

Dependence of optical laser power on disk radius, head-disk spacing and media properties in heat-assisted magnetic recording

2020 ◽  
Vol 26 (11) ◽  
pp. 3371-3376
Author(s):  
Tan D. Trinh ◽  
Sukumar Rajauria ◽  
Robert Smith ◽  
Erhard Schreck ◽  
Qing Dai ◽  
...  
Keyword(s):  
Magnetic Recording ◽  
Laser Power ◽  
Disk Radius ◽  
Heat Assisted Magnetic Recording ◽  
Optical Laser ◽  
Disk Spacing

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%.

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.

Experimental Study of Nanoscale Head-Disk Heat Transfer In Heat-Assisted Magnetic Recording

2021 ◽  
Author(s):  
Qilong Cheng ◽  
David B. Bogy
Keyword(s):  
Heat Transfer ◽  
Silicon Wafer ◽  
Magnetic Recording ◽  
Laser Exposure ◽  
Heat Assisted Magnetic Recording ◽  
Contact Sensor ◽  
Higher Temperature ◽  
Dc Current ◽  
Fly Height ◽  
Head Temperature

Abstract To study the nanoscale heat transfer and laser-related protrusions in heat-assisted magnetic recording (HAMR), we performed static touchdown experiments between HAMR waveguide heads and non-rotating media such as a silicon wafer and a recording disk with an AlMg substrate. During the static touchdown, the laser element is energized with DC current and the embedded contact sensor (ECS) is used to monitor the head temperature. The experimental results show that the thermal fly-height control (TFC) touchdown power decreases with increasing laser current. Meanwhile, the head temperature increases due to the laser heating. From this the ECS resistance rise induced by the laser is extracted. The results show that the silicon wafer dissipates heat effectively under the laser exposure, while the AlMg-substrate disk undergoes a higher temperature rise, which in turn heats the head.

Stress Induced Permanent Magnetic Signal Degradation of Perpendicular Magnetic Recording System

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
Sung-Chang Lee ◽  
Soo-Youl Hong ◽  
Na-Young Kim ◽  
Joerg Ferber ◽  
Xiadong Che ◽  
...  
Keyword(s):  
Magnetic Recording ◽  
Hard Disk Drives ◽  
Magnetic Layer ◽  
Mechanical Damage ◽  
Hard Disk ◽  
Disk Drive ◽  
Magnetic Signal ◽  
Perpendicular Magnetic Recording ◽  
Signal Degradation ◽  
The Media

Model scratches of the size found in hard disk drives are produced under controlled conditions at a series of applied loads on both longitudinal magnetic recording (LMR) media and perpendicular magnetic recording (PMR) media using a diamond tip. The scratches are created at low speed, eliminating thermal considerations from the interpretation of the media response. Nanoindentations are produced as well. The scratches and indentations are characterized by atomic force microscope (AFM), magnetic force microscope (MFM), and also by the same magnetic reader and writer used in an integrated hard disk drive (HDD). A comparison of the response of PMR and LMR media shows the PMR media to have larger scratches and greater magnetic signal degradation than LMR media for a given scratch load. The extent of magnetic damage, as measured by MFM, is greater than the extent of surface mechanical damage, as measured by AFM. Analysis of scratches using the HDD reveals that the magnetic damage is irreversible and permanent damage in magnetic layer, which is confirmed by cross section transmission electron microscope image. The experiments reveal the mechanism for magnetic scratch erasure in the absence of thermal effects. This understanding is expected to lead to improved designs for mechanical scratch robustness of next-generation PMR media.

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