Using Ensemble Waveform Analysis to Compare Heat Assisted Magnetic Recording Characteristics of Modeled and Measured Signals

Hernández, Stephanie; Lu, Peilin; Granz, Steven; Krivošı́k, Pavol; Huang, Pin-Wei; Eppler, Walter; Rausch, Tim; Gage, Edward C.

doi:10.1109/tmag.2016.2612230

Cited by 34 publications

(14 citation statements)

References 12 publications

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“…Despite HAMR being proposed and investigated for around 15 years, a complete understanding of the functioning of these devices necessary for the introduction into the market is lacking [2,[12][13][14][15][16]. Moreover, engineering the medium by combining ferromagnets with different properties [4,17] and improving the head design can yield further increase in the storage density without compromising the reliability of the device [18].…”

Section: Introductionmentioning

confidence: 99%

Magnetization dynamics of granular heat-assisted magnetic recording media by means of a multiscale model

et al. 2020

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Heat-assisted magnetic recording (HAMR) technology represents the most promising candidate to replace the current perpendicular recording paradigm to achieve higher storage densities. To better understand HAMR dynamics in granular media we need to describe accurately the magnetization dynamics up to temperatures close to the Curie point. To this end we propose a multiscale approach based on the Landau-Lifshitz-Bloch (LLB) equation of motion parametrized using atomistic calculations. The LLB formalism describes the magnetization dynamics at finite temperature and allows us to efficiently simulate large system sizes and long time scales. Atomistic simulations provide the required temperature dependent input quantities for the LLB equation, such as the equilibrium magnetization and the anisotropy and can be used to capture the detailed magnetization dynamics. The multiscale approach makes it possible to overcome the computational limitations of atomistic models in dealing with large systems, such as a recording track, while incorporating the basic physics of the HAMR process. We investigate the magnetization dynamics of a single FePt grain as a function of the properties of the temperature profile and applied field and test the LLB results against atomistic calculations. Our results prove the appropriateness and potential of the approach proposed here where the granular model is able to reproduce the atomistic simulations and capture the main properties of a HAMR medium.

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Section: Introductionmentioning

confidence: 99%

Magnetization dynamics of granular heat-assisted magnetic recording media by means of a multiscale model

et al. 2020

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“…By repeating the writing and reading process on 50 different randomly initialized granular media, we are able to calculate the SNR with the methods of Ref. [9]. The readback signal of the same bit sequence on 50 different media is shown in Fig.…”

Section: Snr Calculationmentioning

confidence: 99%

Systematic parameterization of heat-assisted magnetic recording switching probabilities and the consequences for the resulting SNR

Slanovc

Vogler

Muthsam

et al. 2019

Journal of Applied Physics

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The signal-to-noise ratio (SNR) of a bit series written with heat-assisted magnetic recording (HAMR) on granular media depends on a large number of different parameters. The choice of material properties is essential for the obtained switching probabilities of single grains and therefore for the written bits' quality in terms of SNR. Studies where the effects of different material compositions on transition jitter and the switching probability are evaluated were done, but it is not obvious, how significant those improvements will finally change the received SNR. To investigate that influence, we developed an analytical model of the switching probability phase diagram, which contains independent parameters for, inter alia, transition width, switching probability and curvature. Different values lead to corresponding bit patterns on granular media, where a reader model detects the resulting signal, which is finally converted to a parameter dependent SNR value. For grain diameters between 4 and 8 nm, we show an increase of~10 dB for bit lengths between 4 and 12 nm, an increase of~9 dB for maximum switching probabilities between 0.64 and 1.00, a decrease of~5 dB for downtrack-jitter parameters between 0 and 4 nm and an increase of 1 dB for reduced bit curvature. Those results are furthermore compared to the theoretical formulas for the SNR. We obtain a good agreement, even though we show slight deviations.

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“…The writing process is repeated for 50 different randomly initialized granular media. The SNR is then computed from the read-back process with the help of a SNR calculator provided by SEAGATE [37]. The SNR is analysed for areal densities of 2 to 5 Tb/in 2 .…”

Section: Areal Densitymentioning

confidence: 99%

Improving the signal-to-noise ratio for heat-assisted magnetic recording by optimizing a high/low Tc bilayer structure

Muthsam

Slanovc

Vogler

et al. 2019

Journal of Applied Physics

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We optimize the recording medium for heat-assisted magnetic recording by using a high/low T c bilayer structure to reduce AC and DC noise. Compared to a former work, small Gilbert damping α = 0.02 is considered for the FePt like hard magnetic material. Atomistic simulations are performed for a cylindrical recording grain with diameter d = 5 nm and height h = 8 nm. Different soft magnetic material compositions are tested and the amount of hard and soft magnetic material is optimized. The results show that for a soft magnetic material with α SM = 0.1 and J ij,SM = 7.72 × 10 −21 J/link a composition with 50% hard and 50% soft magnetic material leads to the best results. Additionally, we analyse how much the areal density can be improved by using the optimized bilayer structure compared to the pure hard magnetic recording material. It turns out that the optimized bilayer design allows an areal density that is 1 Tb/in 2 higher than that of the pure hard magnetic material while obtaining the same SNR. arXiv:1907.05027v1 [physics.app-ph]

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Using Ensemble Waveform Analysis to Compare Heat Assisted Magnetic Recording Characteristics of Modeled and Measured Signals

Cited by 34 publications

References 12 publications

Magnetization dynamics of granular heat-assisted magnetic recording media by means of a multiscale model

Magnetization dynamics of granular heat-assisted magnetic recording media by means of a multiscale model

Systematic parameterization of heat-assisted magnetic recording switching probabilities and the consequences for the resulting SNR

Improving the signal-to-noise ratio for heat-assisted magnetic recording by optimizing a high/low Tc bilayer structure

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