Browsing by Subject "HAMR"

Now showing 1 - 4 of 4
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    Development and Characterization of Magnetostrictive GaFe and Plasmonic Gold Thin Films
    (2015-04) Estrine, Eliot
    As device sizes continue to shrink into the nano-scale, material development becomes increasingly important. This presents new deposition and characterization challenges which must be overcome to produce the next generation of devices. Magnetostrictive GaFe (galfenol) is one such material in which development of deposition and characterization techniques is necessary to enable new MEMS devices. In addition, plasmonic gold Near Field Transducers (NFTs) used in Heat Assisted Magnetic Recording (HAMR) require new characterization options to understand device failure modes as well as new gold deposition processes to improve device reliability. While these applications are very different, the underlying material deposition and characterization challenges involving thin film crystallinity are very similar. Magnetostriction measurements of electrodeposited galfenol show that it is possible to achieve thin films of this material over a wide range of compositions using electrodeposition. In addition, grain refinement in gold was achieved through alloying which shows the potential to create more robust thin films while maintaining gold's desirable plasmonic properties. Finally, advanced characterization processes using Electron Back Scatter Diffraction (EBSD) were also developed to analyze thin film crystal structure and its role in NFT stability. These results will further progress in the fields of MEMS and HAMR as well as provide the basis for identifying and solving materials challenges in the future.
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    Effects of Skew Angle and Transition Curvature in HAMR Hard Disk Drives
    (2017-05) Cordle, Michael
    Continued areal density growth in hard disk drives (HDD) is becoming increasingly difficult to achieve as Perpendicular Magnetic Recording (PMR) approaches the super paramagnetic limit of ~1Tb/in2. Heat-Assisted Magnetic Recording (HAMR) is on the verge of becoming the next generation of high-density recording technology. Understanding the physical mechanisms behind the unique recording characteristics will be a critical step in the maturity of HAMR technology as it continues to make progress towards production. A notable difference between HAMR and PMR that has drawn a lot of recent attention is the curved shape of a recorded transition. Minimizing transition curvature is understood to be crucial for improving ADC, and current studies have shown that it could be imposing a significant limitation for HAMR. Here, we provide a comparison of HAMR and PMR ADC profiles in an HDD. We explore a new technique proposed for capturing magnetization footprint images through HDD testing, and take full advantage of a significantly improved cycle time to apply a statistical treatment to experimental curvature data to provide a quantitative analysis of factors that impact transition curvature in HAMR and PMR HDDs. We identify geometric effects resulting from skew angle that correlate well to changes in transition curvature. We also show the impact of laser power on transition curvature, and discuss how an understanding of this information can be used to quickly identify uncontrolled variables in an experiment.
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    Heat Assisted Magnetic Recording: Light-Matter Interaction in the Deep Subwavelength Regime
    (2019-01) Ghoreyshi, Ali
    The necessity for low price data storage in emerging Cloud technologies suggests that the Hard Disk Drives (HDDs) will continue to remain the dominant storage technology. To keep up with demands, the hard disk drive industry provided ∼ 40% annual average areal density growth rate over the past 60 years. However, the areal density of current perpendicular magnetic recording technology tends to saturate at ∼ 1.5 Tb/in2. Heat Assisted Magnetic Recording (HAMR) has been considered as the most promising candidate to increase the areal density of HDDs up to 10 Tb/in2. This improvement in the areal density requires employing several aspects of physics - optics, thermal conduction, magnetism, and mechanical control - simultaneously at the smallest regime that a device could operate with the current fabrication technologies. In addition to technological aspects, HAMR provides the opportunity to investigate physical phenomena at the length scale that was rarely investigated before. In this thesis, the light-matter interaction is investigated at the deep subwavelength regime: near the validity limits of macroscopic Maxwell’s equations. First, it is demonstrated that, using plasmonic near-field transducers, light can be focused in an area much smaller than diffraction limit (/100). At this regime, it is demonstrated that the ubiquitous Effective Medium Theory (EMT) breaks down and cannot be used for modeling the interaction between a localized beam and composite structures such as HAMR media. Indeed, the fundamental assumptions of EMT are only valid when the size of the optical beam is much larger than the feature size of composite structures. Instead, by assuming a constant field inside the inhomogeneous phase and neglecting hot spots, an impedance model is proposed for modeling and designing patterned recording media. For the case of the granular recording layer, it is demonstrated that randomness in shape, size, and position of recording grains can lead to localization of depolarization fields. This localization is similar to Anderson localization of electronic wavefunctions in a random potential. In addition, it is demonstrated that for the case of plasmonic particles, random hopping of photons between Localized Surface Plasmonic Polaritons (LSPPs) modes of the system can lead to Anderson localization of the light in the deep subwavelength regime. Finally, the resulting impacts of these localized modes are investigated on the randomness in the absorption of different recording grains. In fact, random absorption can lead to ∼ 3% variation in the temperature of the grains (σT ≈ 3%), which is comparable to the effect of σTc: the common source of transition noise in the recording process.
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    High Anisotropy Magnetic Materials for Data Storage and Spintronic Memory
    (2018-01) Quarterman, Patrick
    Data storage technologies that utilize magnetic materials for storage are key for both increasing areal density of storage in traditional hard disk media and providing low energy alternatives to traditional CMOS technology through spintronic memory and logic devices. Spintronic memory relies on the spin of an electron rather than charge and is a promising candidate for achieving non-volatility which can provide dramatic energy savings. A key challenge for magnetic based storage is achieving 10 nm or smaller feature sizes while retaining thermal stability. This requires development of magnetic thin films with large magnetocrystalline anisotropy. Switching the magnetization of high anisotropy magnetic materials requires large Oersted field or spin current. One way to decrease the switching energy is to lower the anisotropy during the switching process with an applied strain or heat. This scheme retains thermal stability during storage and makes write energies feasible from a technological aspect. Development of suitable high anisotropy materials at sub 10 nm scale has proved difficult due to limitations on traditional thin film growth methods, nanoscale effects, and additional requirements on materials for memory applications. The effect of a static strain on the magnetic anisotropy is well understood, but less so for application in devices which require fast switching and high cycling. The other approach to lowering switching energies is to use magnetic materials with small magnetization, such as Mn-based compounds. I will discuss my experiments to advance understanding of: development of FePt for HAMR media, effect of strain assisted switching on the spin state of FePt, and development of novel high anisotropy Mn-based materials with low magnetization. Finally, I will present my experimental realization of Ru as the 4th room temperature ferromagnetic element. Ru has been predicted to become ferromagnetic when placed into a metastable tetragonal or cubic phase. This new phase of Ru also has potential to achieve the requirements for a viable spintronic device. I will show my work on the realization of the tetragonal phase Ru using seed layer engineering in thin films, and its associated ferromagnetic properties.