Download or read book The Role of Heat Assisted Magnetic Recording in Future Hard Disk Drive Applications written by Diego A. Méndez de la Luz and published by . This book was released on 2004 with total page 140 pages. Available in PDF, EPUB and Kindle. Book excerpt: (Cont.) portable consumer electronics, such as PDAs, cell phones, music players, digital cameras, etc. make a relatively modest but fast growing market for ultrahigh areal density HAMR-based HDDs. HAMR-based HDD for portable applications could very well be a disruptive technology in the magnetic recording industry. Companies that intend to profit from this technology need to invest on its development and must try to be first-to-volume production to benefit from economies of scale and to build the necessary expertise that could give them leadership roles in future magnetic recording.

Download or read book A Study of the Head Disk Interface in Heat Assisted Magnetic Recording Energy and Mass Transfer in Nanoscale written by Haoyu Wu and published by . This book was released on 2018 with total page 114 pages. Available in PDF, EPUB and Kindle. Book excerpt: The hard disk drive (HDD) is still the dominant technology in digital data storage due to its cost efficiency and long term reliability compared with other forms of data storage devices. The HDDs are widely used in personal computing, gaming devices, cloud services, data centers, surveillance, etc. Because the superparamagnetic limit of perpendicular magnetic recording (PMR) has been reached at the data density of about 1 Tb/in^2 , heat assisted magnetic recording (HAMR) is being pursued and is expected to help increase the areal density to over 10 Tb/in^2 in HDDs in order to fulfill the future worldwide data storage demands. In HAMR, the magnetic media is heated locally (~50nm x 50nm) and momentarily (~10ns) to its Curie temperature (~750K) by a laser beam. The laser beam is generated by a laser diode (LD) and focused by a near field transducer (NFT). But the energy and mass transfer at high temperature from the laser heating can cause potential reliability issues. The design temperature of the NFT is much lower than the media’s Curie temperature. However, the distance between the NFT and the media is less than 10nm. As a result, the heat can flow back from the media to the NFT, which is called the back-heating effect. This can cause undesired additional temperature increase on the NFT, shortening its lifetime. Additionally, depletion, evaporation and degradation can happen on the lubricant and the carbon overcoat (COC) layer of the media. The material can transfer from the media to the head at high temperature and cause solid contamination on the head, adversely affecting its reliability. Since the laser heating in HAMR happens at nanoscale spatially and temporally, it is difficult to measure experimentally. In this dissertation, a comprehensive experimental stage, called the Computer Mechanics Laboratory (CML)-HAMR stage, was built to study different aspects of HAMR systems, including the heat and mass transfer in the head-disk interface during laser heating. The CML-HAMR stage includes an optical module, a spinstand module and a signal generation/acquisition module. And it can emulate the HAMR scenario. The head’s temperature was measured during the laser heating using the stage and heads with an embedded contact sensor (ECS). It was estimated, based on a linear extrapolation, that the ECS temperature rise is 139K, 132K, 127K and 122K when the disk is heated to the Curie temperature (~750K) and the head-disk clearance is 0nm, 1nm, 2nm and 3nm, respectively. The heating effect of the ECS was also studied and a related heat transfer experiment was performed. The normalized ECS self heating temperature rise, an indicator of the heat transfer in the head-disk interface (HDI), was measured. It was concluded that the heat transfer coefficient across the HDI strongly depends on the width of the gap size, especially when the gap size is smaller than 1nm. The head disk interaction during the laser heating was studied using a waveguide head, i.e., a HAMR head without the NFT. It showed that the laser heating can cause head surface protrusion. This lowers the fly-height (FH) and results in early touchdown (TD). It was shown that the ratio of touchdown power (TDP) change to the laser current is 0.3mW/mA. The dynamics of the head also changes during the laser heating. It was found that the magnitude of the 1st-pitch-mode vibration on the head increases over time both in short term and long term. The accumulation of material transferred to the head was also investigated. It was found that the solid contamination caused by the laser heating forms in the center of the waveguide. The round-shaped contamination formed on the head surface after laser heating. Finally the disk lubricant reflow after laser heating was studied. In the experiment, a beam of free space laser shines on the rotating disk at different laser powers, disk rotating speeds and repetitions. Then the disk was examined by an optical surface analyzer (OSA). It was found that 80% of the displaced lubricant recovers within 20 minutes. A simulation was also performed. The experiments and the simulation are in good agreement.

Download or read book Heat Assisted Magnetic Recording written by Samarth Bhargava and published by . This book was released on 2015 with total page 114 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this dissertation, we address the burgeoning fields of diffractive optics, metals-optics and plasmonics, and computational inverse problems in the engineering design of electromagnetic structures. We focus on the application of the optical nano-focusing system that will enable Heat-Assisted Magnetic Recording (HAMR), a higher density magnetic recording technology that will fulfill the exploding worldwide demand of digital data storage. The heart of HAMR is a system that focuses light to a nano- sub-diffraction-limit spot with an extremely high power density via an optical antenna. We approach this engineering problem by first discussing the fundamental limits of nano-focusing and the material limits for metal-optics and plasmonics. Then, we use efficient gradient-based optimization algorithms to computationally design shapes of 3D nanostructures that outperform human designs on the basis of mass-market product requirements. In 2014, the world manufactured ~1 zettabyte (ZB), ie. 1 Billion terabytes (TBs), of data storage devices, including ~560 million magnetic hard disk drives (HDDs) [1]. Global demand of storage will likely increase by 10x in the next 5-10 years, and manufacturing capacity cannot keep up with demand alone. We discuss the state-of-art HDD and why industry invented Heat- Assisted Magnetic Recording (HAMR) [2][3] to overcome the data density limitations. HAMR leverages the temperature sensitivity of magnets, in which the coercivity suddenly and non- linearly falls at the Curie temperature. Data recording to high-density hard disks can be achieved by locally heating one bit of information while co-applying a magnetic field. The heating can be achieved by focusing 100 [mu]W of light to a ~30nm diameter spot on the hard disk. This is an enormous light intensity, roughly ~100,000,000x the intensity of sunlight on the earth's surface! This power density is ~1,000x the output of gold-coated tapered optical fibers used in Near-field Scanning Optical Microscopes (NSOM), which is the incumbent technology allowing the focus of light to the nano-scale. Even in these lower power NSOM probe tips, optical self-heating and deformation of the nano- gold tips are significant reliability and performance bottlenecks [4][5]. Hence, the design and manufacture of the higher power optical nano-focusing system for HAMR must overcome great engineering challenges in optical and thermal performance. There has been much debate about alternative materials for metal-optics and plasmonics to cure the current plague of optical loss and thermal reliability in this burgeoning field. We clear the air. For an application like HAMR, where intense self-heating occurs, refractory metals and metals nitrides with high melting points but low optical and thermal conductivities are inferior to noble metals. This conclusion is contradictory to several claims and may be counter-intuitive to some, but the analysis is simple, evident and relevant to any engineer working on metal-optics and plasmonics. Indeed, the best metals for DC and RF electronics are also the best at optical frequencies. We also argue that the geometric design of electromagnetic structures (especially sub- wavelength devices) is too cumbersome for human designers, because the wave nature of light necessitates that this inverse problem be non-convex and non-linear. When the computation for one forward simulation is extremely demanding (hours on a high-performance computing cluster), typical designers constrain themselves to only 2 or 3 degrees of freedom. We attack the inverse electromagnetic design problem using gradient-based optimization after leveraging the adjoint-method to efficiently calculate the gradient (ie. the sensitivity) of an objective function with respect to thousands to millions of parameters. This approach results in creative computational designs of electromagnetic structures that human designers could not have conceived yet yield better optical performance. After gaining key insights from the fundamental limits and building our Inverse Electromagnetic Design software, we finally attempt to solve the challenges in enabling HAMR and the future supply of digital data storage hardware. In 2014, the hard disk industry spent ~$200 million dollars in R & D but poor optical and thermal performance of the metallic nano-transducer continues to prevent commercial HAMR product. Via our design process, we successfully computationally-generated designs for the nano-focusing system that meets specifications for higher data density, lower adjacent track interference, lower laser power requirements and, most notably, lower self-heating of the crucial metallic nano-antenna. We believe that computational design will be a crucial component in commercial HAMR as well as many other commercially significant applications of micro- and nano- optics. If successful in commercializing HAMR, the hard disk industry may sell 1 billion HDDs per year by 2025, with an average of 6 semiconductor diode lasers and 6 optical chips per drive. The key players will become the largest manufacturers of integrated optical chips and nano- antennas in the world. This industry will perform millions of single-mode laser alignments per day. All academic and industrial players in micro- and nano- optics should excitingly watch what Seagate, Western Digital, HGST and TDK accomplish in the next 5-10 years.

Download or read book Ultra High Density Magnetic Recording written by Gaspare Varvaro and published by CRC Press. This book was released on 2016-03-30 with total page 528 pages. Available in PDF, EPUB and Kindle. Book excerpt: Today magnetic recording is still the leading technology for mass data storage. Its dominant role is being reinforced by the success of cloud computing, which requires storing and managing huge amounts of data on a multitude of servers. Nonetheless, the hard-disk storage industry is presently at a crossroads as the current magnetic recording techno

Download or read book Ultrathin Carbon Based Overcoats for Extremely High Density Magnetic Recording written by Reuben Jueyuan Yeo and published by Springer. This book was released on 2017-06-20 with total page 184 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents the latest research in ultrathin carbon-based protective overcoats for high areal density magnetic data storage systems, with a particular focus on hard disk drives (HDDs) and tape drives. These findings shed new light on how the microstructure and interfacial chemistry of these sub-20 nm overcoats can be engineered at the nanoscale regime to obtain enhanced properties for wear, thermal and corrosion protection – which are critical for such applications. Readers will also be provided with fresh experimental insights into the suitability of graphene as an atomically-thin overcoat for HDD media. The easy readability of this book will appeal to a wide audience, ranging from non-specialists with a general interest in the field to scientists and industry professionals directly involved in thin film and coatings research.

Download or read book Hard Disk Drive written by Abdullah Al Mamun and published by CRC Press. This book was released on 2017-12-19 with total page 359 pages. Available in PDF, EPUB and Kindle. Book excerpt: The hard disk drive is one of the finest examples of the precision control of mechatronics, with tolerances less than one micrometer achieved while operating at high speed. Increasing demand for higher data density as well as disturbance-prone operating environments continue to test designers' mettle. Explore the challenges presented by modern hard disk drives and learn how to overcome them with Hard Disk Drive: Mechatronics and Control. Beginning with an overview of hard disk drive history, components, operating principles, and industry trends, the authors thoroughly examine the design and manufacturing challenges. They start with the head positioning servomechanism followed by the design of the actuator servo controller, the critical aspects of spindle motor control, and finally, the servo track writer, a critical technology in hard disk drive manufacturing. By comparing various design approaches for both single- and dual-stage servomechanisms, the book shows the relative pros and cons of each approach. Numerous examples and figures clarify and illustrate the discussion. Exploring practical issues such as models for plants, noise reduction, disturbances, and common problems with spindle motors, Hard Disk Drive: Mechatronics and Control avoids heavy theory in favor of providing hands-on insight into real issues facing designers every day.

Download or read book Magnetic Recording written by Eric D. Daniel and published by John Wiley & Sons. This book was released on 1998-08-31 with total page 364 pages. Available in PDF, EPUB and Kindle. Book excerpt: "The first magnetic recording device was demonstrated and patentedby the Danish inventor Valdemar Poulsen in 1898. Poulsen made amagnetic recording of his voice on a length of piano wire. MAGNETICRECORDING traces the development of the watershed products and thetechnical breakthroughs in magnetic recording that took placeduring the century from Paulsen's experiment to today's ubiquitousaudio, video, and data recording technologies including taperecorders, video cassette recorders, and computer harddrives. An international author team brings a unique perspective, drawnfrom professional experience, to the history of magnetic recordingapplications. Their key insights shed light on how magneticrecording triumphed over all competing technologies andrevolutionized the music, radio, television and computerindustries. They also show how these developments offeropportunities for applications in the future. MAGNETIC RECORDING features 116 illustrations, including 92photographs of historic magnetic recording machines and theirinventors." Sponsored by: IEEE Magnetics Society

Download or read book Optical Delivery in Energy assisted Magnetic Recording EAMR Systems written by Lingyun Miao and published by . This book was released on 2013 with total page 94 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Energy-assisted magnetic recording (EAMR) is considered one of the most promising future technologies in the hard disk drive (HDD) industry for ultra-high density magnetic recording. The EAMR technique requires the use of a laser beam to define magnetic recording features, where high efficiency optical coupling and delivery of a highly focused optical beam at low cost for large volume manufacturing (LVM) are key challenges in building such systems. Currently there is a huge gap between HDD industry status and the requirement for implementation of EAMR technology. This thesis work intends to provide an effective and feasible optical delivery scheme for EAMR functionality. Specifically, we have proposed the design and fabrication of an on-wafer micro focal lens to achieve high-efficiency optical coupling of an external laser beam into a magnetic read/write head at low cost. The demonstrated fabrication process and robustness analysis results confirm that the on-wafer micro focal lens can meet stringent LVM requirements. An advanced dielectric tapered waveguide is also proposed for delivery of the highly focused beam for EAMR. Three-dimensional finite-difference time-domain (FDTD) simulation results show that specially designed dielectric tapered waveguides can provide higher optical efficiency compared with metallic near field transducers (NFTs), and do not encounter overheating or self-burning issues. We have also demonstrated the feasibility of the integration of an on-wafer micro focal lens with a dielectric tapered waveguide to realize the optical delivery functionality in EAMR systems. The proposed structures can be produced using a standard industry top-down fabrication process, which facilitates the integration of such structures with conventional magnetic head industry manufacturing at low cost. Finally, several specific aspects in EAMR applications have been discussed, including magnetic single bit scale, thermal energy and optical power requirements for EAMR function, and thermal diffusion or heat conduction analysis in EAMR systems. The estimated and analyzed results show that the thesis work promises to achieve magnetic recording density at about 1 Tbit/inch2 for use in next generation hard drives, with the combined use of appropriate recording medium materials satisfying certain thermal properties"--Page vi-vii.

Download or read book Block Trace Analysis and Storage System Optimization written by Jun Xu and published by Apress. This book was released on 2018-11-16 with total page 279 pages. Available in PDF, EPUB and Kindle. Book excerpt: Understand the fundamental factors of data storage system performance and master an essential analytical skill using block trace via applications such as MATLAB and Python tools. You will increase your productivity and learn the best techniques for doing specific tasks (such as analyzing the IO pattern in a quantitative way, identifying the storage system bottleneck, and designing the cache policy). In the new era of IoT, big data, and cloud systems, better performance and higher density of storage systems has become crucial. To increase data storage density, new techniques have evolved and hybrid and parallel access techniques—together with specially designed IO scheduling and data migration algorithms—are being deployed to develop high-performance data storage solutions. Among the various storage system performance analysis techniques, IO event trace analysis (block-level trace analysis particularly) is one of the most common approaches for system optimization and design. However, the task of completing a systematic survey is challenging and very few works on this topic exist. Block Trace Analysis and Storage System Optimization brings together theoretical analysis (such as IO qualitative properties and quantitative metrics) and practical tools (such as trace parsing, analysis, and results reporting perspectives). The book provides content on block-level trace analysis techniques, and includes case studies to illustrate how these techniques and tools can be applied in real applications (such as SSHD, RAID, Hadoop, and Ceph systems). What You’ll Learn Understand the fundamental factors of data storage system performance Master an essential analytical skill using block trace via various applications Distinguish how the IO pattern differs in the block level from the file level Know how the sequential HDFS request becomes “fragmented” in final storage devices Perform trace analysis tasks with a tool based on the MATLAB and Python platforms Who This Book Is For IT professionals interested in storage system performance optimization: network administrators, data storage managers, data storage engineers, storage network engineers, systems engineers

Download or read book Nanostructured Magnetic Materials written by Sathish-Kumar Kamaraj and published by CRC Press. This book was released on 2023-08-21 with total page 297 pages. Available in PDF, EPUB and Kindle. Book excerpt: Functionalized magnetic nanomaterials are used in data storage, biomedical, environmental, and heterogeneous catalysis applications but there remain developmental challenges to overcome. Nanostructured Magnetic Materials: Functionalization and Diverse Applications covers different synthesis methods for magnetic nanomaterials and their functionalization strategies and highlights recent progress, opportunities, and challenges to utilizing these materials in real-time applications. Reviews recent progress made in the surface functionalization of magnetic nanoparticles Discusses physico-chemical characterization and synthesis techniques Presents the effect of the external magnetic field Details biological, energy, and environmental applications as well as future directions This reference will appeal to researchers, professionals, and advanced students in materials science and engineering and related fields.

Download or read book Role of Bit Patterned Media in Future of Hard Disk Drives written by and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The hard disk industry has traditionally stayed competitive by competing on the means of price alone by cutting down aggressively on cost via increase of areal density. Continuing increases in the areal density of hard disk drives will be limited by thermal instability of the thin film medium and is estimated to be limited to about 500Gb/in2. Patterned media, in which data are stored in an array of single.domain magnetic particles, have been suggested as a means to overcome this limitation and to enable recording densities greater than ITb/in2. However, the implementation of patterned media requires fabrication of sub-50-nm features over large areas and the design of recording systems that differ from those used in conventional hard drives. This report discusses the challenges facing patterned media, the fabrication of arrays of ́small magnetic particles and their magnetic properties. The practical implementation of patterned media recording schemes is assessed via technology estimates and cost analysis.

Download or read book Study of Dynamics and Nanoscale Heat Transfer of Head Disk Interface in Hard Disk Drives written by Yuan Ma and published by . This book was released on 2018 with total page 104 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since its introduction in 1956, hard disk drives have become one of the dominant products in the industry of data storage. The capacity of the hard disk drives must keep evolving to store the exploding data generated in the era of big data. This demand pushes the development of technologies including heat assisted magnetic recording (HAMR), microwave assisted magnetic recording (MAMR) and bit-patterned media (BPM) to increase the areal density beyond 1Tb/in2. In the development of these technologies, it is essential to have a clear understanding of the dynamics and nanoscale heat transfer behavior across the head-disk interface. In this dissertation, dynamics and nano-scale heat transfer in the head disk interface are discussed. Experimental study of nano-scale heat transfer is conducted with the specifically designed static touchdown experiment. Simulation strategy that incorporates the wave-based phonon conduction theory was also developed. In the flying condition, correlation between the temperature and head disk spacing was found at both passive flying stage and modulation stage. When the flying height increases due to either disk surface microwaviness or contact induced modulation, head temperature will increase, with a slight time delay, indicating the existence of a cooling effect as the head approaches the disk. The static touchdown experiment, which decouples the complicated air bearing from the nano-scale interface was further designed and performed. The heat transfer behavior across a closing nano-scale gap between head and disk was observed and measured. Experimental and simulation results showed general agreement with the theoretical predictions of the wave based theory for radiation and phonon conduction. The effect of different factors including humidity, air pressure, lubricant layer and disk substrate in the static touchdown experiment were also studied separately. Furthermore, the dynamics of HAMR condition was studied with waveguide heads. The laser induced protrusion was found to be around 1~2 nm in height. The findings of this dissertation could be applied to future HAMR head/media design, and the static touchdown experiment could be potentially improved to be a new approach to measure material conduction coefficient and emissivity with high special resolution.

Download or read book Tribological Performance of the Head Disk Interface in Perpendicular Magnetic Recording and Heat Assisted Magnetic Recording written by Tan Duy Trinh and published by . This book was released on 2019 with total page 185 pages. Available in PDF, EPUB and Kindle. Book excerpt: International Data Corporation (IDC) estimates that hard disk drives will still be the main storage device for storing digital data in the next 10 years, holding approximately 80% of the data inside data centers. To increase the areal density of hard disk drives, the mechanical spacing between the head and disk surface has decreased to approximately 1nm. At such a small spacing, tribology of the head-disk interface, including head-disk contacts, wear, material buildup, and lubricant transfer, become increasingly more important for the reliability of hard disk drives. In addition to small spacing, heat-assisted magnetic recording (HAMR) technology aims to deliver higher areal density recording by heating up the media surface to a few hundred Celsius degrees, facilitating the writing process. High temperature at the head and disk surfaces cause serious reliability issues for the head-disk interface (HDI). Therefore, understanding of the main factors that affect the reliability of the head-disk interface is an essential task. In this dissertation, the effect of bias voltage and helium environment on the tribological performance of the head-disk interface is investigated. To do this, we first simulated the flying characteristics of the slider as a function of bias voltage in air and helium environment. Thereafter, an experimental study was performed using custom built tester located inside a sealed environmental chamber to study the effect of air and helium on wear and lubricant redistribution at the head-disk interface during load-unload. We investigated the effect of bias voltage and relative humidity on wear, material buildup, and nano-corrosion on the slider surface. Finally, we have studied laser current and laser optical power in heat-assisted magnetic recording as a function of operating radius, head-disk clearance, media design, and their effects on the life-time of the head-disk interface. The results of this dissertation provide guidance for the effect of bias voltage, relative humidity, and helium environment on wear, material buildup, corrosion, and lubricant transfer at the head-disk interface. More importantly, our experimental study in heat-assisted magnetic recording leads to a better understanding of the main factors that cause failure of the HAMR head-disk interface. Our results are important for the improvement of the tribological performance and reliability of perpendicular magnetic recording (PMR) and heat-assisted magnetic recording (HAMR) head-disk interface.

Download or read book Role of Bit Patterned Media in Future of Hard Disk Drives written by Vibin Aravindakshan and published by . This book was released on 2007 with total page 61 pages. Available in PDF, EPUB and Kindle. Book excerpt: The hard disk industry has traditionally stayed competitive by competing on the means of price alone by cutting down aggressively on cost via increase of areal density. Continuing increases in the areal density of hard disk drives will be limited by thermal instability of the thin film medium and is estimated to be limited to about 500Gb/in2. Patterned media, in which data are stored in an array of single.domain magnetic particles, have been suggested as a means to overcome this limitation and to enable recording densities greater than ITb/in2. However, the implementation of patterned media requires fabrication of sub-50-nm features over large areas and the design of recording systems that differ from those used in conventional hard drives. This report discusses the challenges facing patterned media, the fabrication of arrays of ́small magnetic particles and their magnetic properties. The practical implementation of patterned media recording schemes is assessed via technology estimates and cost analysis.

Download or read book Acoustically Assisted Magnetic Recording written by Weiyang Li and published by . This book was released on 2015 with total page 134 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the past few decades, magnetic recording has been used as a dominant solution for massive data storage due to its large capacity, excellent reliability and low cost. Nowadays, exponentially increasing user-generated information is creating a huge demand as well as great challenges for high density data storage solutions. For high density magnetic recording, or more specifically, for hard disk drives, the bit size of the recording medium has to be reduced. This requires the medium to have an increased coercivity to avoid data loss due to thermal instability. However, data recording in a high coercivity medium is challenging due to the limited practicable write field. Therefore, the requirements of high coercivity for data stability and low coercivity for writeability are conflicting. During the last 15 years, enormous research and engineering efforts have been invested in heat-assisted magnetic recording and bit-patterned media, endeavoring to solve this contradiction. In this dissertation we take an alternative approach and demonstrate that acoustic wave, or strain wave, could be used to address the tradeoff between writeability and stability. This technique is called acoustically assisted magnetic recording. The physics behind this technique is based on the inverse magnetostriction effect or Villari effect, by which the coercivity of a magnetostrictive material can be modified by strain. In operation, a surface acoustic wave is applied to a recording medium, where the resulting acoustic strain temporarily lowers the coercivity (thus makes it magnetically soft), enabling data to be recorded with a lower write field. The medium regains its high coercivity after the acoustic wave is removed and thus becomes magnetically hard for data stability. An experimental device consisting of an interdigitated transducer is designed and fabricated on a piezoelectric quartz substrate for generating the surface acoustic wave. Galfenol film with high magnetostriction is deposited as the recording medium on the same substrate. The acoustic wave propagates in the galfenol film and the resulting strain is measured by laser interferometry. In the proof-of-principle experiments for acoustically assisted magnetic recording, data are recorded in a strained magnetostrictive medium with a smaller write field than when it is unstrained. The required write field strength is lowered by ~10% with ~100 ppm strain applied to the medium. A curved acoustic transducer is developed to focus the acoustic strain so large change in coercivity can be achieved in the focal spot and to demonstrate that an individual bit can be selectively written in the medium. In hard disk drives, rather than the low coercivity galfenol film, high coercivity material is used as the recording medium. L10 phase Fe50Pt(50-x)Pdx thin film is a promising candidate for next-generation high coercivity recording media and its magnetostriction is characterized regarding to the application of acoustically assisted magnetic recording. It is found that the magnetostriction of Fe50Pt(50-x)Pdx film is dependent on the Pd content. This suggests that the magnetostriction can be controlled and thus optimized by adjusting the film composition. Also, to apply the acoustically assisted magnetic recording technique to the practical hard disk drives, the acoustic transducer should be integrated in the write head and the generated acoustic wave needs to be air coupled from the head to the recording medium. An electromagnetic acoustic transducer is developed to investigate the possibility of coupling the wave through electromagnetic interaction. The investigation of mechanical-magnetic interaction between acoustic waves and magnetostrictive films also leads to applications other than magnetic recording. We demonstrate that various and controllable magnetization patterns such as periodic stripes (10 [micro]m periodicity) and single dot (3 [micro]m diameter) could be written in the magnetostrictive film by creating different acoustic interferences. This could be potentially used in magnetic particle manipulation, spatial light modulation and magnonic signal processing. Also, a surface acoustic wave magnetic field sensor using galfenol thin film is successfully demonstrated. Here, based on the [delta]E effect, the velocity of acoustic wave propagating in the galfenol film is measured to determine the magnetic field. Since galfenol is highly magnetostrictive, a maximum velocity change of 6.4% is achieved, much larger than previously reported results in similar systems.

Download or read book Head disk Interface Study for Heat Assisted Magnetic Recording HAMR and Plasmonic Nanolithography for Patterned Media written by Shaomin Xiong and published by . This book was released on 2014 with total page 184 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Nanotechnology Technology Revolution of 21st Century written by Rathi Rakesh and published by S. Chand Publishing. This book was released on 2009 with total page 296 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nanotechnology