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Rea C.,Recording Head Operations | Holfeld J.,Recording Head Operations | Kalarickal S.,Twin Cities Operations | Benakli M.,Recording Head Operations | And 13 more authors.
IEEE Transactions on Magnetics | Year: 2014

Heat-assisted magnetic recording (HAMR) is a fast evolving technology, and has been established as the next enabler of higher areal density in magnetic recording. After achieving high areal density capability, HAMR drive integration was recently demonstrated. In this paper, we discuss some of the recent learning from component performance and drive integration. We identify a key challenge in HAMR integration: erasure due to thermal background heating. The background heating was introduced to improve near-field transducer reliability and reduce laser power requirement. We present experimental and modeling data on the impact of thermal background, both in the cross-track (adjacent-track erasure) and down-track (self-erasure) dimensions. © 2014 IEEE.

Kiely J.D.,Recording Head Operations | Jones P.M.,Recording Media Operations | Wang H.,Recording Media Operations | Yang R.,Recording Head Operations | And 4 more authors.
IEEE Transactions on Magnetics | Year: 2014

Heat-assisted magnetic recording involves the transfer of energy to the recording medium via optical means. To enable high areal density, the recorded track must be smaller than the diffraction limit of focused light, which is accomplished by using a near-field transducer (NFT) with a corner or peg with small dimension. Energy transfer using such a transducer is a near-field effect, and therefore is highly sensitive to the spacing between the NFT and the medium. Since the recording medium has some surface roughness, there will be a variation in the NFT-to-medium spacing and this will impact the amount of energy transferred from the NFT. We model the effect of Gaussian surface roughness on NFT energy transfer and predict surface temperature variations for a rough surface. In addition, we illustrate how changing the head-medium spacing changes the impact that roughness has on surface temperature variation. We combine these modeled predictions with spinstand measurements of recorded data and conclude that the effect of media roughness results in only limited temperature excursions above the nominal recording medium temperature. © 2014 IEEE.

Hernandez S.,Research Storage Group | Lu P.-L.,Research Storage Group | Granz S.,Research Storage Group | Krivosik P.,Recording Head Operations | And 4 more authors.
IEEE Transactions on Magnetics | Year: 2016

Ensemble waveform analysis is used to calculate signal to noise (SNR) and other recording characteristics from micromagnetically modeled HAMR waveforms and waveforms measured at both drive and spin-stand level. Using windowing functions provides the breakdown between transition and remanence SNR. Also, channel bit density (CBD) can be extracted from the ensemble waveforms using the di-bit extraction method. Trends in both transition SNR, remanence SNR and CBD as a function of ambient temperature at constant track width showed good agreement between model and measurement. Both model and drive-level measurement show degradation in SNR at higher ambient temperatures, which may be due to changes in the down-track profile at the track edges compared to track center. CBD as a function of cross-track position is also calculated for both modeling and spin-stand measurements. The CBD widening at high cross-track offset, which is observed at both measurement and model, was directly related to the radius of curvature of the written transitions observed in the model and the thermal profiles used. © 2015 IEEE.

Hernandez S.,Storage Research Group | Krivosik P.,Recording Head Operations | Huang P.-W.,Recording Media Operations | Eppler W.R.,Recording Head Operations | And 2 more authors.
IEEE Transactions on Magnetics | Year: 2016

The auto-correlation signal-to-noise (ACSN) method is employed on micromagnetically modeled heat-assisted magnetic recording (HAMR) readback waveforms and compared with experimental ACSN data. The breakdown between transition signal-to-noise ratio (SNR) and remanence SNR is provided for both modeled and measured data. Good agreement is observed between both simulated and experimental SNRs as a function of laser power and as a function of linear density. An efficiency factor that relates maximum temperature observed in the media to the applied laser current is obtained by combining the modeled and experimental data. Usage of this methodology provides SNR metrics that allow a reliable comparison of micromagnetic modeling of HAMR recording systems to experimental measurements. © 2016 IEEE.

Rea C.,Recording Head Operations | Scholz W.,Recording Head Operations | Cao L.,Recording Head Operations | Peng C.,Recording Head Operations | And 14 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2014

Recent recording areal density and integrated drive performance demonstrations using Heat Assisted Magnetic Recording (HAMR) suggest that it is a viable technology to succeed conventional magnetic recording. However challenges still remain for the near field transducer, in particular reliability and sufficient thermal confinement. We explore a new NFT design, Near field Transducer Gap (NTG), which offers the potential to mitigate some of the issues in track confinement and thermal profile compared to earlier published studies [4]. The design offers efficiency improvements, and the potential to reduce unwanted background light and heating that can lead to erasure in the writing track, and neighbors. © 2014 SPIE.

Yu Z.,Recording Media Operations | Hwu J.,Recording Media Operations | Liu Y.,Recording Media Operations | Liu Y.,Nanometrics Inc. | And 11 more authors.
Journal of Vacuum Science and Technology B:Nanotechnology and Microelectronics | Year: 2010

The authors have applied spectroscopic ellipsometry optical critical dimension (SE-OCD) measurement to grating templates and imprinted resist patterns with a pitch of 72.6 nm, corresponding to a track density of 350 ktpi (kilotracks per inch) for discreet track recording media. Their experiments indicate that SE-OCD is sensitive in detecting topography features in template profiles. The measurement of imprinted resist pattern is complicated by parameter correlation. Comparison of SE-OCD reported template and imprinted resist profiles can be used to study imprint pattern fidelity. © 2010 American Vacuum Society.

Heyne L.,University of Konstanz | Rhensius J.,University of Konstanz | Ilgaz D.,University of Konstanz | Bisig A.,University of Konstanz | And 9 more authors.
Physical Review Letters | Year: 2010

We use a pump-probe photoemission electron microscopy technique to image the displacement of vortex cores in Permalloy discs due to the spin-torque effect during current pulse injection. Exploiting the distinctly different symmetries of the spin torques and the Oersted-field torque with respect to the vortex spin structure we determine the torques unambiguously, and we quantify the amplitude of the strongly debated nonadiabatic spin torque. The nonadiabaticity parameter is found to be β=0.15±0.07, which is more than an order of magnitude larger than the damping constant α, pointing to strong nonadiabatic transport across the high magnetization gradient vortex spin structures. © 2010 The American Physical Society.

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