The Experts below are selected from a list of 23913 Experts worldwide ranked by ideXlab platform
R H Victora - One of the best experts on this subject based on the ideXlab platform.
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composite media for high density heat assisted Magnetic Recording
2016Co-Authors: Yipeng Jiao, R H VictoraAbstract:A heat assisted Magnetic Recording composite media with a superparaMagnetic writing layer is proposed. The Recording process is initiated in the write layer that is Magnetically softer than the long term storage layer. Upon cooling, the composite structure copies the information from the writing layer to the lower Curie temperature (Tc) storage layer, e.g., doped FePt. The advantages include insensitivity to Tc variance in the storage layer, and thus the opportunity to significantly lower the FePt Tc without the resulting Tc distribution adversely affecting the performance. The composite structure has a small jitter within 0.1 nm of the grain size limit owing to the sharp transition width of the optimized superparaMagnetic writing layer. The user density of the composite structure can reach 4.7 Tb/in.2 for a Gaussian heat spot with a full-width-at-half-maximum of 30 nm, a 12 nm reader width, and an optimized bit length of 6 nm.
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renormalized anisotropic exchange for representing heat assisted Magnetic Recording media
2015Co-Authors: Yipeng Jiao, Zengyuan Liu, R H VictoraAbstract:Anisotropic exchange has been incorporated in a description of Magnetic Recording media near the Curie temperature, as would be found during heat assisted Magnetic Recording. The new parameters were found using a cost function that minimized the difference between atomistic properties and those of renormalized spin blocks. Interestingly, the anisotropic exchange description at 1.5 nm discretization yields very similar switching and magnetization behavior to that found at 1.2 nm (and below) discretization for the previous isotropic exchange. This suggests that the increased accuracy of anisotropic exchange may also reduce the computational cost during simulation.
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exchange coupled composite media for perpendicular Magnetic Recording
2005Co-Authors: R H Victora, Xiao ShenAbstract:Exchange coupled composite (ECC) media has been shown to possess several major advantages relative to conventional perpendicular media, including a reduction in the switching field of approximately a factor two for the same thermal stability and greater insensitivity to easy axis distribution. In this paper, full magnetostatic interactions are included: this allows comparison between the behavior of multigrain thin films and that of isolated grains as presented earlier. Significant results include hysteresis loops for thin films under various conditions including inadequate and excessive intra granular exchange between the hard and soft materials. An important distinction is made between the coercivity and remnant coercivity as a function of angle between applied field and easy axis. A perpendicular Magnetic Recording head is used to compare the shape of effective fields for ECC and conventional perpendicular media. Written transitions in the ECC media appear to be similar to those written in perpendicular media at comparable densities.
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composite media dynamic tilted media for Magnetic Recording
2005Co-Authors: Jianping Wang, R H Victora, W K Shen, Jianmin Bai, J H Judy, Woobin SongAbstract:We designed and fabricated a composite Magnetic Recording medium with exchange decoupled Magnetic grains that consist of two vertically exchange-coupled Magnetic regions (one is Magnetically soft and one is Magnetically hard) as an approach to alleviate the writing field limitation of perpendicular Magnetic Recording heads. A nonMagnetic layer with different thickness was put between the hard and soft layer to tune the exchange coupling. With proper coupling, significant drop of the coercivity field was observed for this composite medium while still maintaining good thermal stability. Better Recording performance was obtained for such medium compared to perpendicular and longitudinal medium. The results have proved the possibility of fabricating a writable Recording medium having an ultrahigh Magnetic anisotropy constant (Ku) value.
Hans Jurgen Richter - One of the best experts on this subject based on the ideXlab platform.
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Direct Measurement of the Thermal Gradient in Heat Assisted Magnetic Recording
2013Co-Authors: Hans Jurgen Richter, C. C. Poon, Gregory Parker, Matteo Staffaroni, O. Mosendz, R. Zakai, Barry Cushing StipeAbstract:In heat assisted Magnetic Recording, the thermal gradient at the Recording point determines the quality of the written transitions. We developed an experimental technique that enables us to find the thermal gradients in both the down- and the cross-track directions, where the laser power is modulated during the Recording process. It is explained in detail how quantitative information on the gradients can be obtained from the measured data. It is found that strong heat-sinking of the media increases the thermal gradient and that the gradient measurement reacts sensitively to the shape of the thermal profile.
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domain wall assisted Magnetic Recording
2006Co-Authors: Yu A Dobin, Hans Jurgen RichterAbstract:Using numerical and analytical microMagnetics the authors calculated the switching fields and energy barriers of the composite (exchange spring) Magnetic Recording media, which consist of layers with high and low magnetocrystalline anisotropies. The authors demonstrate that the ultimate potential of the composite media is realized if the interfacial domain wall fits inside the layers. The switching occurs via domain wall nucleation, compression in the applied field, depinning, and propagation through the hard/soft interface. The authors demonstrate that the domain wall assisted Magnetic Recording offers up to a threefold areal density gain over conventional single layer Recording.
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domain wall assisted Magnetic Recording
2006Co-Authors: Yu A Dobin, Hans Jurgen RichterAbstract:Using numerical and analytical microMagnetics we calculated the switching fields and energy barriers of the composite (exchange spring) Magnetic Recording media, which consist of layers with high and low magnetocrystalline anisotropy. We demonstrate that the ultimate potential of the composite media is realized if the interfacial domain wall fits inside the layers. The switching occurs via domain wall nucleation, compression in the applied field, de-pinning and propagation through the hard/soft interface. This domain wall assisted switching results in a significant reduction of the switching field without substantial decrease of the for thermal activation energy barrier. We demonstrate that the Domain Wall Assisted Magnetic Recording (DWAMR) offers up to a three-fold areal density gain over conventional single layer Recording.
Yipeng Jiao - One of the best experts on this subject based on the ideXlab platform.
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composite media for high density heat assisted Magnetic Recording
2016Co-Authors: Yipeng Jiao, R H VictoraAbstract:A heat assisted Magnetic Recording composite media with a superparaMagnetic writing layer is proposed. The Recording process is initiated in the write layer that is Magnetically softer than the long term storage layer. Upon cooling, the composite structure copies the information from the writing layer to the lower Curie temperature (Tc) storage layer, e.g., doped FePt. The advantages include insensitivity to Tc variance in the storage layer, and thus the opportunity to significantly lower the FePt Tc without the resulting Tc distribution adversely affecting the performance. The composite structure has a small jitter within 0.1 nm of the grain size limit owing to the sharp transition width of the optimized superparaMagnetic writing layer. The user density of the composite structure can reach 4.7 Tb/in.2 for a Gaussian heat spot with a full-width-at-half-maximum of 30 nm, a 12 nm reader width, and an optimized bit length of 6 nm.
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renormalized anisotropic exchange for representing heat assisted Magnetic Recording media
2015Co-Authors: Yipeng Jiao, Zengyuan Liu, R H VictoraAbstract:Anisotropic exchange has been incorporated in a description of Magnetic Recording media near the Curie temperature, as would be found during heat assisted Magnetic Recording. The new parameters were found using a cost function that minimized the difference between atomistic properties and those of renormalized spin blocks. Interestingly, the anisotropic exchange description at 1.5 nm discretization yields very similar switching and magnetization behavior to that found at 1.2 nm (and below) discretization for the previous isotropic exchange. This suggests that the increased accuracy of anisotropic exchange may also reduce the computational cost during simulation.
D Weller - One of the best experts on this subject based on the ideXlab platform.
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review article fept heat assisted Magnetic Recording media
2016Co-Authors: D Weller, Gregory Parker, O. Mosendz, A Lyberatos, D Mitin, Nataliia Y Safonova, M AlbrechtAbstract:Heat-assisted Magnetic Recording (HAMR) media status, requirements, and challenges to extend the areal density (AD) of Magnetic hard disk drives beyond current records of around 1.4 Tb/in.2 are updated. The structural properties of granular high anisotropy chemically ordered L10 FePtX-Y HAMR media by now are similar to perpendicular CoCrPt-based Magnetic Recording media. Reasonable average grain diameter ⟨D⟩ = 8–10 nm and distributions σD/D ∼ 18% are possible despite elevated growth temperatures TG = 650–670 °C. A 2× reduction of ⟨D⟩ down to 4–5 nm and lowering σD/D < 10%–15% are ongoing efforts to increase AD to ∼4 Tb/in.2. X = Cu ∼ 10 at. % reduces the Curie temperature TC by ∼100 K below TC,bulk = 750 K, thereby lowering the write head heat energy requirement. Multiple FePtX-Y granular layers with Y = 30–35 vol. % grain-to-grain segregants like carbides, oxides, and/or nitrides are used to fully exchange decouple the grains and achieve cylindrical shape. FePt is typically grown on fcc MgO (100) seedlay...
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nanomanufacturing strategy and system design for nanoscale patterned Magnetic Recording medium
2005Co-Authors: Dmitri Litvinov, D Weller, Grant C Willson, John C WolfeAbstract:The long-term goal of this project is to demonstrate ultra-high density Magnetic data storage using nanoscale patterned Magnetic Recording medium, a single-grain-per-bit Recording paradigm, where the randomness inherent to conventional polycrystalline Magnetic Recording medium is eliminated through lithographic patterning and self-assembly methods. The program combines several diverse research efforts to explore the fundamentals of nanoMagnetics, Recording physics of patterned media, nanoscale self-assembly, and the limits of resists and lithography. The specific objectives are: 1) to develop patterned Magnetic Recording media design guidelines for "next generation" information storage systems; 2) to develop highly exchange-coupled patterned media materials using combinatorial materials synthesis; 3) to develop manufacturing strategies at the nanometer scale using a combination of Atom/Ion Beam Lithography and Step-and-Flash Imprint Lithography; 4) to demonstrate a prototype of a functional patterned medium at the scale of 25 nm/bit or 1 Terabit/in 2 ; and 5) to extend the technology to the superparaMagnetic limit at 3-4 nm/bit using a novel patterning approach based on self-assembled nanomask lithography. Prototype Recording systems will be built to evaluate the functionality (e.g., write/read efficiency, signal-to-noise ratio, bit error rates) of the patterned media. The proposed technology is expected enable the $23 billion information storage industry to continue its record-setting growth rate for the next 7-15 years. It should also lead to dramatic storage device miniaturization, acting as a catalyst for a wealth of new mobile computing applications. The nanofabrication toolset will offer an immediate benefit to Magnetic random access memory and Magnetic quantum cellular automata, and thus has the potential to transform the integrated circuit industry. The toolset can be applied to molecular and nanoelectronic integrated systems as well.
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the physics of ultra high density Magnetic Recording
2001Co-Authors: M L Plumer, Johannes Van Ek, D WellerAbstract:1 Introduction to MicroMagnetic Recording Physics.- 2 Microstructure of Longitudinal Media.- 3 Magnetization Dynamics and Thermal Fluctuations in Fine Grains and Films.- 4 Measurement of Dynamic Properties in Thin-Films.- 5 Thermal Effects in High-Density Recording Media.- 6 Dynamic Effects in High-Density Recording Media.- 7 Patterned Media.- 8 Perpendicular Recording Media.- 9 Self-Assembled Magnetic Nanoparticle Arrays.- 10 Theory of Magnetotransport for Magnetic Recording.- 11 Recording Head Design.
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extremely high density longitudinal Magnetic Recording media
2000Co-Authors: D Weller, Mary Frances DoernerAbstract:▪ Abstract Areal density progress in Magnetic Recording is largely determined by the ability to fabricate low-noise, granular thin lm media with sufficient stability against thermal agitation to warrant long-term data storage. A key requirement is a medium microstructure with small, Magnetically isolated grains to establish optimal macro- and micro-Magnetic properties. A lower bound for the minimal average grain diameter, compatible with thermal stability, is imposed by the write field capability of the Recording head. It is 10–12 nm assuming maximal writeable coercivities of 400 kA/m (5000 Oe). These are already achieved in today's state-of-the-art CoCr-based thin lm alloy media, leaving little room for further improvements and density gains based on continued grain size reduction. A threefold reduction in grain diameter, however, translating into a tenfold increase in areal density is theoretically possible if write field constraints can be overcome, allowing utilization of Magnetically harder alloys. T...
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thermal stability of longitudinal Magnetic Recording media
1999Co-Authors: A Moser, D Weller, Mary Frances DoernerAbstract:Thermal processes may limit the lifetime of stored data and ultimately the achievable areal density in Magnetic Recording. To quantify this important problem, we have studied a series of state-of-the-art thin film CoPtCr longitudinal Recording media samples with thicknesses ranging between 5.5 and 13 nm. Static write/read tester experiments are used to measure the remanent coercivity of these films as a function of the applied Magnetic field pulse width, which is varied in the range of nanoseconds to seconds. The data are analyzed in terms of an inverse slope parameter, 1/C, which in the framework of a Neel-Arrhenius model is equivalent to the familiar stability ratio EB/kBT. This ratio is then correlated with signal decay measurements, performed over a time range after writing of 2.8 s to ≈1 day. Both measurements are carried out at variable temperatures, T, between 300 and 390 K. The onset of strong signal decay in low density square wave bit patterns occurs when 1/C drops below about 36.
Yurii Skourski - One of the best experts on this subject based on the ideXlab platform.
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a new highly anisotropic rh based heusler compound for Magnetic Recording
2020Co-Authors: Gerhard H Fecher, Yu Pan, Kaustuv Manna, Johannes Kroder, Ajay Jha, Xiao Wang, S Agrestini, Javier Herreromartin, Manuel Valvidares, Yurii SkourskiAbstract:The development of high-density Magnetic Recording media is limited by superparamagnetism in very small ferroMagnetic crystals. Hard Magnetic materials with strong perpendicular anisotropy offer stability and high Recording density. To overcome the difficulty of writing media with a large coercivity, heat-assisted Magnetic Recording was developed, rapidly heating the media to the Curie temperature Tc before writing, followed by rapid cooling. Requirements are a suitable Tc , coupled with anisotropic thermal conductivity and hard Magnetic properties. Here, Rh2 CoSb is introduced as a new hard magnet with potential for thin-film Magnetic Recording. A magnetocrystalline anisotropy of 3.6 MJ m-3 is combined with a saturation magnetization of μ0 Ms = 0.52 T at 2 K (2.2 MJ m-3 and 0.44 T at room temperature). The Magnetic hardness parameter of 3.7 at room temperature is the highest observed for any rare-earth-free hard magnet. The anisotropy is related to an unquenched orbital moment of 0.42 μB on Co, which is hybridized with neighboring Rh atoms with a large spin-orbit interaction. Moreover, the pronounced temperature dependence of the anisotropy that follows from its Tc of 450 K, together with a thermal conductivity of 20 W m-1 K-1 , make Rh2 CoSb a candidate for the development of heat-assisted writing with a Recording density in excess of 10 Tb in.-2 .
