Characterization of Laser-Induced Protrusion in HAMR by the Burnish Method

Zhang, Zhenyi; Liu, Kowang; Jin, Eric X.; Dovek, M.; Kiely, James D.; Nakada, Osamu; Wong, Pak Kin; Chiah, Vincent Man Fat; Liu, Xiao Ming

doi:10.1109/tmag.2015.2468217

Cited by 11 publications

(2 citation statements)

References 8 publications

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“…The thermal protrusion and temperature rise responses versus time as a function of input laser power and NMS are studied in [144]. Burnish method is used to report laser induced protrusion [107]. Nevertheless, as pointed out by Schreck et al [108] [149].…”

Section: Discussionmentioning

confidence: 99%

“…The spacing between NFT and media is one of the most important parameters to control during the recording process because it will affect the energy transfer efficiency [105]. Many research works have been done to have a better understanding of various protrusions [106][107][108][109][110]. However, the accurate direct real-time measurements of protrusions and NMS remain a very difficult task due to the tiny size of the NFT.…”

Section: Nft Designmentioning

confidence: 99%

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Servo pattern enhancements for high areal density hard disk drives

Kun¹

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The growth of areal density (AD) in hard disk drive (HDD), which measures the data bits per unit area, has slowed down considerably in recent years from the average of 30% annual increase rate achieved in past decades. The main reason is that the current perpendicular magnetic recording (PMR) technology has reached its bottleneck of the so-called superparamagnetism. In the meantime, HDD is facing a strong competition and high market share challenge from solid state drive (SSD). As a result, HDD industry is striving to improve the AD with a few technologies such as shingled magnetic recording (SMR), two-dimensional magnetic recording (TDMR), heat-assisted magnetic recording (HAMR) and bit patterned media (BPM). Among all of these, HAMR is the most viable and promising technology to bring the AD beyond a few terabyte/in 2 level in the coming decade. When the AD is > 1 terabyte/in 2 , the track width is expected to be smaller than a few tens of nanometers. Being a mechanical device, ever decreasing track width has imposed more stringent requirements on the servo system for the better track-following performance of read and write operations. This thesis first focuses on writing good quality servo patterns such as burst field and repeatable run-out (RRO) compensation field under HAMR writing conditions. The HAMR writing mechanism is fundamentally different from the PMR. For PMR, the written-in signal quality is mainly determined by the strength and the gradient of the writing magnetic field. However, for HAMR, although the writing magnetic field is important, the dominating factor for recording quality is determined by the media thermal profile. The media thermal profile is in turn determined by the thermal properties of the media stack and the thermal power delivered to the media. Given the write head design, and especially the near field transducer (NFT), the thermal power delivered to the media can be controlled through input laser power and the spacing between the NFT and the media. Unfortunately, the NFT-to-media

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Section: Discussionmentioning

confidence: 99%

Section: Nft Designmentioning

confidence: 99%

Servo pattern enhancements for high areal density hard disk drives

Kun¹

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Measurement of angstrom-level laser induced protrusion using touchdown in heat-assisted magnetic recording

Cheng

Wang

Sakhalkar

et al. 2020

Applied Physics Letters

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In heat-assisted magnetic recording (HAMR), a laser is employed above the read-write transducer to provide energy to the media, lowering its coercivity. However, the laser also brings thermal energy diffusion inside the slider and induces an extra angstrom-level protrusion, which we call laser-induced protrusion (LIP). The LIP needs to be taken into consideration in HAMR due to the significance of head-media spacing. This paper focuses on laser heating on the millisecond timescale during flying in the HAMR conditions. When the laser is turned ON for milliseconds, the LIP forms in the short term (∼μs) and fly height change (FHC) happens in the long term (∼ ms) due to the crown/camber change, resulting in a smaller touchdown power (TDP). Thus, the touchdown power change (ΔTDP) is measured and the LIP is isolated using the time constants. A component-level HAMR stage is used to study the effects of laser-on time, laser current, and linear velocity on the ΔTDP. The experimental results show that the FHC needs ∼ 28 ms to reach the steady state and that the protrusion size presents a two-stage linear relation with the laser current separated by a threshold. The LIP size is reduced by about half when operating from 12 m/s to 24 m/s.

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Modelling and compensation for laser induced transients to improve HAMR writing quality

Wang

et al. 2016

2016 Asia-Pacific Magnetic Recording Conference Digest (APMRC)

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Characterization of Laser-Induced Protrusion in HAMR by the Burnish Method

Cited by 11 publications

References 8 publications

Servo pattern enhancements for high areal density hard disk drives

Servo pattern enhancements for high areal density hard disk drives

Measurement of angstrom-level laser induced protrusion using touchdown in heat-assisted magnetic recording

Modelling and compensation for laser induced transients to improve HAMR writing quality

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