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%.

Investigation of the Local Temperature Increase From the Magnetization Decay for Heat Assisted Magnetic Recording

2013 ◽  
Author(s):  
Shaomin Xiong ◽  
David Bogy
Keyword(s):  
Refractive Index ◽  
Magnetic Recording ◽  
Curie Point ◽  
Laser Heating ◽  
Temperature Increase ◽  
Laser Power ◽  
Local Temperature ◽  
Thermally Stable ◽  
Heat Assisted Magnetic Recording ◽  
The Media

The areal data density of magnetic recording hard disk drives (HDDs) increases year by year, following a trend similar to Moore’s law. However, the increase is not unbounded and there are some physical limits. As the density increases, the size of each magnetic grain shrinks. Finally the magnetic grain will be no longer thermally stable due to what is termed superparamagnetism. Above this point, the magnetic storage would be not reliable because the magnetic grains’ orientations fluctuate randomly. To increase magnetic recording density to more than 1 Tb/in2 and break this limit, heat assisted magnetic recording (HAMR) is proposed. In HAMR systems, a more thermally stable magnetic material, one with higher coercivity, will be used as a recording layer. But the coercivity of this material at room temperature is so high that it is difficult for the writer to switch the magnetic orientation with current magnetic transducers. However, the coercivity drops sharply if the temperature is raised close to the Curie temperature. In HAMR systems, a laser is proposed as the means to heat the disk to the Curie point. Simultaneously the magnetic field is applied from the writer to switch the magnetic bits. The success of the magnetic switching is very sensitive to the media temperature [2]. If the temperature is too low compared with the Curie point, it will not be able to write any information into the media. Conversely, heating the media over the Curie point requires more energy and may bring a greater challenge for the head disk interface (HDI). It is very important to understand the local temperature distribution during the laser heating and to calibrate the laser power input for HAMR writing. Some work has been done to evaluate the temperature increase using both numerical and experimental methods [3, 4]. Tagawa et.al. observed the disk refractive index change during laser heating and compared it with the change under conventional oven heating. This is a good method to calibrate the laser power and get the average temperature but it has some limitations for getting the accurate temperature distributions because of the averaging effect for the refractive index measurement by ellipsometry.

Thermal decomposition and desorption of PFPE Zdol on a DLC substrate using quartic bond interaction potential

RSC Advances ◽  
2015 ◽  
Vol 5 (85) ◽  
pp. 69651-69659 ◽  
Author(s):  
S. K. Deb Nath
Keyword(s):  
Thermal Decomposition ◽  
Interaction Potential ◽  
Magnetic Recording ◽  
Magnetic Layer ◽  
Hard Disk ◽  
Carbon Overcoat ◽  
Heat Assisted Magnetic Recording ◽  
Reading And Writing ◽  
Bond Interaction ◽  
Laser Rays

In heat assisted magnetic recording (HAMR) system, heating of the hard disk magnetic layer is carried out by applying laser rays during the movement of the read/write head over the carbon overcoat for the purpose of reading and writing on its magnetic layer.

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.

Performance benefits from pulsed laser heating in heat assisted magnetic recording

2014 ◽  
Vol 115 (17) ◽  
pp. 17B701 ◽  
Author(s):  
B. X. Xu ◽  
Z. H. Cen ◽  
J. H. Goh ◽  
J. M. Li ◽  
Y. T. Toh ◽  
...  
Keyword(s):  
Magnetic Recording ◽  
Laser Heating ◽  
Pulsed Laser ◽  
Heat Assisted Magnetic Recording ◽  
Pulsed Laser Heating

Laser Current Studies in Heat-Assisted Magnetic Recording

2019 ◽  
Author(s):  
Tan D. Trinh ◽  
Sukumar Rajauria ◽  
Robert Smith ◽  
Erhard Schreck ◽  
Qing Dai ◽  
...  
Keyword(s):  
Laser Diode ◽  
Magnetic Recording ◽  
Optical Power ◽  
Disk Surface ◽  
Integrated System ◽  
Nanometer Scale ◽  
Outer Diameter ◽  
Heat Assisted Magnetic Recording ◽  
Fully Integrated ◽  
Inner Diameter

Abstract In heat-assisted magnetic recording (HAMR), optical power from a laser diode mounted on the slider is used to heat up a nanometer scale area on the disk surface to approximately 450°C, facilitating the writing process. Controlling optical power or current that is applied to the laser diode in HAMR is a critical task. In this study, a fully integrated system of HAMR heads and disks is used to study laser current as a function of the magnetic write width (MWW), the operating radius, and the head-disk clearance. Our experimental results show that the laser current is a linear function of the magnetic write width and the head-disk clearance. As the operating radius increases from the inner diameter to the outer diameter of the disk, the laser current increases by approximately 20%.

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.

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