HDDs have been just one of the most dominant data storage solution with high-density recording volume yet reasonably low cost.

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From: advances in chemical Engineering, 2011

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Thomas Wei Jie Kwok, ... Beng Wah Chua, in reference Module in materials Science and also Materials Engineering, 2020

Case research 3 – Helium tough Disk drive Casing

Hard disk journey (HDD) modern technology has been steadily enhancing throughout the years. Among the an ext recent innovations is a helium fill HDD. By instead of air v helium, the disks experience much less drag when spinning, allowing for diluent disks (allowing for more disks per HDD) and also faster spin speeds. Helium fill HDDs because of this have a bigger capacity, quicker read and write speeds and are also quieter (Seagate, 2016). However, the challenge facing the sector was to build a an approach to store the helium in the HDD there is no leaking out over time.

HDD basic plates room traditionally manufactured from cast Al alloys via HPDC. However, that was found that cast Al HDD basic plates consisted of interconnected porosity microchannels i beg your pardon would permit helium come leak the end (Seagate, 2016). Traditional HDD casings space not hermetic and therefore not an ideal for this application.

Possible techniques to create a completely dense, zero porosity base plate incorporate full machining native extruded wrought alloy feedstock or forging with subsequent machining yet both procedures are considerably an ext expensive than HPDC. To express casting, however, is one alternative technique with a costing level similar to HPDC. While the is certainly feasible for squeeze casting to satisfy the requirements for a hermetic base plate, the preform design is no without challenges. The cross-section of the hard disk baseplate reflects a thin base through a thick wall around it. Thin-to-thick and also thick-to-thin sections are daunting from a die filling perspective but likewise affects the uniform applications of press (Fig. 7(e) and (f)).

To certain laminar dice filling properties, the beat speed can be slowed to permit even pour it until it is full of the thick walls. If the punch rate is also fast, then jetting would occur in the thin-to-thick sections, resulting in severe entrapped gas porosity. However, the slow-moving filling rate also permits the thin base to completely solidify before the walls can be filled. The an outcome is the the beat ‘bottoms out’ and also when press is applied, the punch presses versus an incompressible heavy base and the thick walls receive small to no pressure. This results in galling and extreme die wear along the base and a large number of spreading defects such as shrinkage porosity in the walls which cannot be tolerated in this specific application.

The equipment to this conundrum consists of countless incremental changes. Firstly, the preform architecture should be changed to allow better flow and also minimize jetting even with a fast punch speed. This consisted of rounding out sharp corners and also merging several thick sections with each other for example. Secondly, the punch deserve to be split into number of inserts. Die springs or disc springs can be placed behind each insert to manage the quantity of pressure on the area under every insert. Once the beat “bottoms out” ~ above the thin base, the springs on the beat insert directly over will compress, allowing the punch to continue pushing downwards and apply pressure on the special walls. In several shrinkage prone spots, a second hydraulic mechanism may also be employed.


Alexander King, in critical Materials, 2021

Giant magnetoresistance

Nine years from exploration to commercialization

Hard disk cd driver (HDDs) were very first introduced together a tool for computer random access memory (RAM) by the IBM coporation, group in 1954. They became the dominant data storage style in mainframe computers in the 1960s and also quickly take it over an individual computers after castle were an initial introduced right into this ar by IBM, in 1983. The data thickness of HDDs has increased steadily over time, through the fostering of a variety of new technologies: The an initial hard decaying in a PC had a volume of 10 MB in a 5¼ in. Format, and today’s units market multiple terabytes in drives as little as 2½ in. The capacity to detect magnetic field alters on a tiny scale has actually been a major contributor come this advancement in data density: small magnetic domains can be packed very closely together on the surface of the tough disk, yet the magnetic flux linked with every binary number of data additionally depends top top the domain size. Small data bits create correspondingly minute amounts of magnetic flux, and they can only be detected by highly sensitive detectors.

Early read/write systems for HDDs—along with other magnetic recording devices—relied top top the current induced in a coil the wire as it moved through the changing magnetic field created by the taped data. This mechanism is minimal at small sizes due to the fact that the induced existing in the field coil relies on the amount of the magnetic flux and also the number of turns in the coil. Together the data bits shrank, the flux declined, and the number of turns in the field coils additionally had to be decreased to make them smaller, and also the readable existing in the check out head intimidated to shrink below the detection limit.

An alternative an innovation for reading data native a magnetic storage unit is the usage of magnetoresistance; one effect very first discovered by lord Kelvin in 1856. The electrical resistance the some materials can adjust when they are placed in a magnetic field, depending upon the alignment that the present with the ar direction. The resistance that a little conductor is likewise easier come measure, using an externally applied voltage, than is the existing induced in a very tiny electromagnetic generator. The resistance detection an approach gains the advantage over existing detection as soon as the tools are scaled down to very small sizes.

IBM began emerging HDD systems based upon anisotropic magnetoresistance (AMR) in 1969 and also brought its first one right into production 14 years later, in 1983. This is a moderately fast material-dependent technology adoption, yet it is also fair to keep in mind that that was based on a discovery made 127 years earlier, and the materials involved and also the basics of sensor architecture were currently well known before IBM started its advancement efforts. The advance time shows the intricacy of bringing brand-new technologies to market in the high-technology sector, and the reality that the grandfather drives were, in reality, radically different tools than the induction current HDDs the they replaced.

A transformation in the science of magnetoresistance developed in 1988 when large magnetoresistance (GMR) was discovered independently by groups working in France and Germany <15, 16>, a exploration for i m sorry Albert Fert and Peter Grünberg common the 2007 Nobel compensation in physics. GMR occurs in conductive thin-film superlattices the iron and chromium with individual layers about 10 atom layers thick, and also it produces lot larger changes of resistance 보다 AMR, leading to greater sensitivity and the ability to scale magnetic memory to much smaller sizes. GMR was commercialized in IBM’s HDDs in 1997, 9 years after the was very first discovered, and it quickly ended up being the industry standard for these pervasive memory devices.

IBM’s rapid adoption of GMR technology doubtless benefited native its previous occupational on adapting AMR to work-related in HDDs, however the instead of of AMR by GMR still required a significant R&D effort.

The rate with i m sorry the new material systems associated in both AMR and also GMR cd driver were adopted owes a good deal to a large economic steering force, with very solid competition amongst the HDD manufacturers of the time. IBM additionally benefitted from close links to between its manufacturing divisions and its own world-class an easy research capacity (a routine that was demonstrably qualified of developing its very own Nobel compensation winners).


O. Ozatay, ... P.M. Braganca, in comprehensive Nanoscience and Technology, 2011

4.18.4.4 summary and Conclusions

HDD modern technology offers a reliable and low-cost equipment to storing big amounts that data but future enhancements in the breakthrough of HDDs present a range of challenges. In the existing granular media, one little bit of information is stored within multiple magnetic grains and also the thermal security of the data is identified by the thermal security of every grain. Because 2000, exceptional improvements have actually been brought about by the development of CoCrPt:oxide-based PMR together with very sensitive GMR and also TMR sensors. However, an essential limits the the physics underlying the HDD modern technology make the expansion of this trend right into the following decade really challenging. In particular, the design of media having good thermal stability, writability, and also SNR (readability) is quickly approaching basic limits. Finding more suitable products could help to achieve fine and also uniform grains and then achieve an excellent signal-to-noise ratio. In search of materials or methods to attain high magnetic anisotropy in recording media could assist to improve thermal stability. Far-ranging work is also carried the end on brand-new multilayer concepts like exchange coupled constant (ECC). However, how far the areal density can at some point be thrust with continuous granular media is an open up question of good technological and also economical consequences. Many experts at this time expect the to reach close come 1 Tb in−2, which at current annual growth rates can be got to within the following 3–5 years.


Therefore, prospects because that data areal densities over 1 Tb in−2 indicate novel advanced media schemes either using a patterned media or energy-assisted record (Figure 30). On the one hand, the patterned media approach proposes one of two people to physically characterized track within existing granular media (DTM) or come lithographically characterized magnetic islands (BPM). In the extreme situation of little pattern media, one magnetic island corresponds to one bit, who volume can be increased contrasted with the grain dimension in standard media, result in raised thermal stability. Top top the various other hand, energy-assisted magnetic recording offers heat, or a high-frequency magnetic field to temporarily lower the reversal ar of granular high-KU media while preserving high stability at remainder or throughout the reading process. Because that each among these alternative approaches several vital issues continue to be to be solved, and also which one will administer the many promising and extensible entry into the Tb in−2 era the magnetic record is really much an open up question at this point. However, the difficulties at 10 Tb in−2 will most more than likely require the two disputed approaches to be combined, the is, BP media v various forms of energy-assisted writing. There room finally plenty of technical challenges as well with regard come the characterization and analysis of the different species of media discussed here. Several of them indicate the specific estimation of the SFD, analysis of the reversal modes, and switching nature of media grains or nanodots. As the volume of the tool storing a bit of info shrinks more into the nanoscale regime, these measurement obstacles require novel tools and also techniques. Consequently, magnetic recording modern technology even 110 years after its innovation still is evolving at a rapid pace and also offers a rich field for an easy research and technical invention.


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Giuseppe Florio, in recommendation Module in products Science and Materials Engineering, 2021

Hard disc Drives

Hard disk drives are among the most usual technologies supplied nowadays due to the fact that of their capacity and also performances (Spaldin, 2011). The device is comprised by several contents where the magnetic layers used for storage is combination to a rigid substrate (prevention that shocks, decreased vibrations and thermal stability), one underlayer (isolation of magnetic grains, avoidance of inter-particle interactions, manage of magnetic flux during the writing process) and an overcoat (protecting interface in between the magnetic layer and also the review or create heads).

Information warehouse is performed using the domains of the magnetic material with the orientation that magnetization representing the physics realization of a single bit v two logical states. The warehouse layer is comprised by a slim film (20 nm special or less) v magnetically anisotropic grains having actually a very small diameter (10 nm).

The compose head is generally made that a ferromagnetic or ferrimagnetic product surrounded by a coil with a time varying electric current flowing with it. The present generates a variable magnetic flux the penetrates right into the magnetic layer. As soon as the magnetic field is eliminated the magnetization the the tool remains, therefore storing the bit. The recording of data deserve to be perpendicular or longitudinal through respect to the plane of the magnetic material. The former method has been introduced in order to increase the amount on details stored. Together a issue of fact, one of the key drawbacks in magnetic storage is the fact that to reduce the dimension of the seed in the record layer increases the probability of reversing the magnetization of a region due to thermal fluctuation (superparamagnetic effect). This worry is an ext pronounced in the situation of longitudinal storage. Perpendicular storage deserve to circumvent this worry by enhancing the thickness of magnetic elements and the use of hard magnetic materials with bigger value of coercivity, therefore less perceptible to heat fluctuation.

In stimulate to carry out the analysis operation, one can use two various methods. In principle, the inductive an approach used for writing deserve to be additionally used for retrieving the information. On the other hand, the fields in the domains of the magnetic class are little and, thus, the signal inductively created in the review head is small. The use of Anisotropic magnetoresistance (see section “Magnetoresistance”) has actually led come the advancement of a new generation that reading facets called dual-stripe top that resolve this problem: the analysis head can sense the variation of the magnetic field in the storage layer through the adjust in the electrical resistance that the magnetoresistive element. Finally, the development of devices based on Giant magnetoresistance (as turn valves) used as incredibly sensible field sensors have furtherly enhanced the reading ability of heads and improved speed of data transfer.


Computer difficult disk drives room a prime instance of where performance renovations are traceable to improvements in long-term magnets. In a addressed disk drive long-term magnets are supplied in the spindle motor, in the actuator that drives the read/write heads (generally termed the voice coil motor (VCM)), and the latch assembly (see figure 4). Disk cd driver nowadays have actually a 2.5, 3, or 3.5 in form factor, as focus has switched native miniaturization to making the storage volume of the journey as huge as possible.



The accessibility of high-remanence rare-earth magnets has permitted the disk drive designer come reduce dramatically the size of the VCM, as only a little volume the magnet product is required, and to decrease accessibility times. Decaying drives usage a high-grade sintered Nd2Fe14B, showing typically a remanence of 1.4 T, an intrinsic coercivity of 1190 kA m-1, and an energy product that 360 kJ m-3. One or two magnets might be employed, with a complete weight that 15.5 g, and also return poles space made that low-carbon steel. Spindle motors may use sintered or polymer-bonded material, with the latter regularly favored as it have the right to be conveniently molded to shape. Spindle motor rate is essential as the greater the rate the much shorter the look for time. High-capacity drives discovered in file-servers have actually a spindle speed of 10 000 rpm, if drives offered in desktops and notebooks have actually speeds of 7200 rpm and 5400 rpm, respectively. Removable cartridge cd driver of 100–250 MB capacity use direct motors and also polymer-bonded Nd2Fe14B, to keep their expense down. It must be listed that small disk drives used in video cameras and lap-top computer systems are themselves being replaced by solid state memory, in countless high-performance products.


Ian Hutchings, Philip Shipway, in Tribology (Second Edition), 2017

9.6 Magnetic Data Storage

The magnetic tough disk drive, a vital component for data storage in desktop computer and laptop computers and larger-scale data servers, has actually increased in capacity by a phenomenal extent due to the fact that it was very first introduced in the 1950s. The binary data is stored as details encoded right into magnetized regions on the surface of quickly spinning disks. In modern-day drives the data is written to the disk and read from that by a read/write head that is supported on a an extremely thin film of air—a gas bearing—as the decaying spins beneath it. The first disk journey to usage aerodynamically-supported heads, the IBM 1302 the 1965, was the size of a little car and also stored 120 MB (1 megabyte = 106 bytes) in ~ a cost (in 2017 terms) of virtually US$2 million; in contrast, a palm-sized drive of the current day stores numerous TB (1 terabyte = 1012 bytes) for about $100, and data capacity is most likely to continue to increase. Present data densities exceed 1 terabit per square customs (approximately 1.5 gigabits per square millimetre; 1 byte = 8 bits), identical to each bit of information taking increase a square area 25 nm by 25 nm. This dramatic boost in storage capacity has actually been achieved by a gradual reduction in the size and also a change in orientation the the magnetized domains in i beg your pardon the data is stored and also by developments in the physics the the read–write process, but it has additionally involved a exceptional reduction in the ‘flying height’ that the head end the disc surface. A little gap in between the head and the magnetic material is needed to accomplish high lateral resolution in the reading and writing processes. The earliest drives had a head flying height of about 6 μm, but in modern drives this has been reduced to much less than 10 nm, a feat that demands not only an accurate modelling of the gas film and head dynamics but likewise the production of disk surface of excessive flatness and also smoothness.


Figure 9.33 mirrors the common internal plan of a hard disk drive, with the head at the finish of its assistance arm; each surface of the disks in a multi-disk ridge is accessed by a separate head. The disk commonly has a diameter the 63.5 or 88.9 mm (2.5 or 3.5 inches) and rotates in ~ 7200 rpm. The read/write function is carry out by a very tiny active an ar embedded into a larger slider, 1–2 mm across. The design of the slider deserve to be complex, as portrayed in Fig. 9.34 which reflects one example. The surface of the slider is patterned v steps and also ledges frequently 0.5–2 μm in height that space designed to create a circulation of aerodynamic pressure throughout the slider surface which raises the slider above the decaying in a secure manner. Aerodynamic lubrication plot in the wedge-shaped wait film in between the stationary slider and also the relocating disk surface. The net push difference between the lower and upper surfaces of the slider outcomes in a vertical force that is balanced by the bending that a flexural facet in the support arm, and the paris height and attitude are controlled by the equilibrium between the aerodynamic and bending forces. Feedback instrument are used to regulate the head position an extremely accurately. Although many drives right now operate in air, there are potential benefits in terms of reduced flying height and lower frictional drag in utilizing a gas with reduced viscosity, and helium is because of this used in a couple of applications.




The disk platters themselves provide fantastic example that surface engineering for sensible applications, combine mechanical, data storage and also tribological properties. Multilayer structures, as shown in Fig. 9.35, room deposited top top a substrate made from rolling aluminium–magnesium alloy (AA5083; 96% Al, 4% Mg) i beg your pardon is extremely polished, v a usual roughness Ra that 15–25 nm. Electroless plating (see section 7.4.1) is used to deposit a reasonably thick (10 μm) nickel–phosphorus layer (90% Ni, 10% P) i beg your pardon acts together a difficult substrate because that the functional magnetic layers and also is likewise polished (to 0.5–2 nm Ra). The phosphorus rises the hardness that the deposit. A succession of an extremely thin class is then deposited through PVD processes: a sublayer of chromium (~ 50 nm) come bond the magnetic layer come the Ni–P layer; the magnetic class in i beg your pardon the data is save on computer (~ 30 nm the a facility alloy, often Co-based, occasionally itself through a multilayer structure); and also an even thinner (~ 15 nm) hydrogenated diamond-like carbon (DLC) overcoat which protects the magnetic layer from mechanically damage. Finally very thin (~ 1 nm) class of lubricant (typically perfluoropolyether, with an extremely low vapour pressure) is deposit by dip-coating indigenous solution, again to defend the disk surface from damages if the head touches it. Both the lubricant layer and also the DLC layer administer some corrosion defense to the magnetic film.



B. Rauschenbach, ... L. Roux, in reference Module in products Science and Materials Engineering, 2016

3.1.1.2 Source/drain (S/D) an ar doping

S/D HDD p+−type PII doping for PMOS machine is additionally an applications that is provided in manufacturing for dram manufacturing. The advantage of PII contrasted to beam heat implanter is the high surface concentration of the doping profile. B2H6 is usually provided for the precursor, due to the fact that the co-implanted fluorine through BF3 might lead to call reliability problems. Compared to the use of beam line implanter, plasma doping reduces the call resistance by ~50% and increases the conducting existing IDS through ~15% (Qin et al., 2007). Typical process conditions room biases that 4–6 kV and dose roughly 2×1016 cm−2.

Some other development have additionally been performed come optimize the S/D BC (buried contact) doping. Right here the goal is come compensate impurity ns during call area etching and cleaning, and increase impurity concentration at the metal/Si interface without negatively impacting junction qualities such together VT, SVT, break down voltages, and also leakages. Qin et al. (2012) demonstrated a reduction of ~70% of the contact resistance the devices using a PII implant of B2H6 through the call opening just before the PVD Ti/CVD W-based metallization.


R. Seidel, ... P.F. Nealey, in directed Self-assembly of Block Co-polymers for Nano-manufacturing, 2015

6.6.2 Bit-patterned media

The development of tough disk drive counts on scaling the feature size of regular structures to do high-density data warehouse possible. However, superparamagnetism implemented a border for the the smallest grain size in the traditional granular media. Instead, each bit in bit-patterned media (BPM) is lithographically patterned and also the magnetic islands are comparably larger in dimension than the seed in this typical case. This permits for the palliation of signal-to-noise ratio and also provides thermal stability. The challenge shifts come the manufacturing of patterns with high area density, beyond 1 Tbits/in.2, which falls in the resolution selection of self-assembling BCPs.


DSA deserve to be incorporated in the initial measures to create templates for succeeding pattern transfer or replication. The sporadic chemical fads for DSA the BCPs were ready by a rotating E-beam tool. After DSA, the fads with thickness multiplication were moved to a substrate, serving together a grasp template because that nanoimprinting to produce a high volume of replicates and then disks v magnetic media (Figure 6.24). Two geometries of BCPs have actually been explored to fulfill the density demand of BPM end 1 Tbits/in.2. The an initial are the hexagonally close-packed cylinders (Hellwig et al., 2010) or spherical (Yang et al., 2013; Xiao et al., 2013) BCP domains, which offers the greatest area density. The 2nd geometry uses an orthogonal line cut to fabricate a rectangular unit.


Although the close-packed patterns administer the greatest area density of features, the integration v recording systems has discovered some difficulties. It has actually been suggested to use rectangle-shaped bits through a bit aspect ratio (the proportion of the cross-track come the down-track pitch) higher than 1. V a line cut strategy (Ruiz et al., 2011), rectangular little cells can be fabricated via a double imprinting process. Briefly, one submaster have the right to be patterned through circumferential lines and also the second is patterned with radial present (Figure 6.25).


Figure 6.25. (a) Schematic representation of a twin imprint process to produce rectangular features. Two “submaster” templates, one with circumferential stripes and also a second one v radial lines, room imprinted top top a different “master” template. The intersection the the two sets outcomes in rectangle-shaped features. (b) Circumferential block copolymer lines v a 27-nm full pitch. (c) Sidewall spacer heat doubling native block copolymer lines v a 41-nm full pitch (top that image) come 20.5-nm pitch lines after heat doubling (bottom). (d) High bit facet ratio rectangular functions imprinted in withstand by the master template.

Other 보다 the bits, servo trends are also required to be developed in BPM for the head to locate data precisely. Servo patterns are mainly irregular in shape, and also thus need a certain integration strategy with the BCP assembly. For the chevron design, very first an EBL thin pattern was defined and the BCPs tended to follow the bends with various angles. Due to the fact that of the free-energy penalty, defects formed at the chevron apexes. Accordingly, extr vertical lines were added at the junction the horizontal tracks and also chevrons. This helps to minimization the defective area in ~ the interfaces by half, as shown in number 6.26 (Liu et al., 2011c). Subsequently, a brand-new integration method, termed “offset burst,” to be proposed and also the position error signal for track following can be encoded (Lille et al., 2012). From the EBL step, a set of circumferential present was purposely shifted follow me the cross-track direction. One strategy to combine servo and data patterns is to operation a separate patterning process after the DSA the data region. This commonly is not favored because the registration of the two patterns would be extremely difficult.


Figure 6.26. Chevron design schematics and also resulting lamellar patterns. For architecture I and also II schematics (shown in ~ the top), the solid lines represent the e-beam fads at a duration of 2 L0 = 54 nm, when the dotted lines stand for lamellae interpolation providing 2 × density multiplication. In style II extra upright e-beam patterns were added. SEM pictures of the result lamellae ordering are displayed to the right. The red dashed lines indicate the boundaries in between defective and also nondefective areas. The widths that the design II defective locations are smaller sized as a result of the extr vertical patterns.

Alexander King, in critical Materials, 2021

Rare earth magnets

As us look for resources of crucial materials, we need to recognize targets the contain significant amounts of the materials that us seek and also are likewise viable as recycling businesses. The biggest volume that rare planet magnet materials, accounting for about 40% that the market, goes into industrial electric motors and generators, which also contain large quantities that copper and ferrous alloys, v a fairly small lot on nonrecyclable material. This devices, however, generally have long company lives and are retired infrequently. Your collection and delivery to recycling centers involve deliver over lengthy distances, and also the gadgets are of change size and also form, making their disassembly daunting to automate.

The second largest single component that the market for rare planet magnets is in tough disk drives, bookkeeping for approximately 16% that the market in 2014. The demands of this market can readjust quite quickly as HDDs are supplanted by other technologies and also the form factors that the HDDs shrink v their ever-increasing memory density.

The instead of of HDDs by solid-state memory predominantly affects consumer and also business computers, when HDDs stay the technology of selection in big data centers due to the fact that they are durable over large numbers of read/write operations: The life the solid-state storage is limited to a fixed variety of such operations, and also data centers store and transfer information at prices that would certainly burn the end solid-state RAM very quickly. Data centers proliferate v the expansion of cloud computing services and also Internet-based social and also business applications, therefore they represent good targets for metropolitan mining: they contain huge amounts that rare-earth magnet material in a small geographical footprint, and a usual data center can retire hundreds of thousands of practically identical hard disk drives every year. These HDDs contain far-reaching amounts of priceless metals along with aluminum and ferrous alloys, so they have actually potential together a recycling organization venture.


There space two set of rare earth permanent magnets in a usual hard disc drive. Among these is in the spindle motor, which turns the disc assembly, and also the various other makes up the voice coil motor, which positions the read/write head (Fig. 7.4). In a 3½ in. HDD, the magnets in the voice-coil motor total between 10 and 20 g that sintered neodymium magnet material with little or no dysprosium added; because that a 2½ in. Journey the voice-coil magnets total approximately 2.5 g <10>. Spindle motors contain smaller quantities of resin-bonded neodymium magnet product that is normally not considered economical come recover.


Early efforts to recuperate magnets native HDDs were based upon manual disassembly. A typical HDD is opened up by removing about 10 screws from its lid, and also then several much more must be gotten rid of to extract the voice-coil and also spindle motors. The spindle motor is more complex to extract, and because it contains a smaller magnet 보다 the voice-coil motor, it is typically ignored in manual processes. An competent disassembler through an electrical screwdriver may be able to extract the voice-coil magnet assembly from an HDD in much less than 10 min. For a 3½ in. HDD at the high end of the magnet dimension range, this assembly would certainly contain about $0.45 precious of REEs at 2018 prices, so extract REEs from about 10 HDDs every hour does no pay the hourly fairy of a low-skilled worker in a developed country, and disassembly is just the very first step in recovering the worth of the rare earth. After extract the voice-coil magnet assembly, several more steps are compelled to recover the magnet materials, consisting of separating the magnets from your μ-metal backing, demagnetizing, stripping the coating, and preparing the material for reuse through some process such together grinding or hydrogen decrepitation <11>. Smaller-format HDDs take about the exact same amount that time come disassemble as larger ones, however they contain considerably less magnet material, therefore the economics of hand-operated recycling thrive progressively worse together HDD technology advances.

Coproduction of other recyclable parts and materials, consisting of precious metals, aluminum, and also ferrous alloys, help the economics, but the quantities of this also decrease as the drive sizes shrink.

Alternatives to hands-on disassembly have actually been arisen to alleviate the price of extracting rare earth permanent magnets native HDDs. A Hitachi-developed device tumbles HDDs in a north to ease and/or eliminate the screws, and this is report to boost the disassembly rate into the range of numerous units every hour. An automatically system developed at Oak Ridge nationwide Lab in collaboration with the an essential Materials institute identifies the location of the voice-coil assembly and slices turn off the corner of the journey that has it <12>: a single maker system have the right to extract voice-coil magnets at rates of hundreds of units every hour, with minimal labor costs, although a larger capital investment is forced for this kind of machinery.

An alternate approach is come shred entire HDDs there is no separating their components and then extract the various materials through chemistry methods. When this technique has lower costs at the front end of the process, it may involve more facility chemical separations additional downstream. It likewise suffers indigenous the an obstacle that shredded magnets accumulate right into “hairballs” along with shards of various other magnetizable materials and entrapped nonmagnetic ones, and also they stick to the ferrous metal materials in the shredding machines.


There room several technological choices for recycling HDDs, each v its own benefits and disadvantages. The breakthrough of a successful commercial system will depend on optimizing overall value recovery including all of the recoverable materials and also disposal of the materials whose value does no justify recovery. The International electronics Manufacturing to plan (iNEMI) has convened a job team consisted of of HDD manufacturers, data facility operators, and also recyclers, in addition to government and university researchers, to identify a system that achieves this goal and also then build a pilot variation of the <13, 14>. When this is a occupational in progress, it has several features that skinny in favor of its eventual success:

It is a pragmatic technique that concentrates on total value recovery from a solitary class that device, rather than simply recycling vital materials.

The team includes significant contributors throughout the whole life bike of the an equipment and the products that the contains, and also it has access to leading-edge labs and researchers.

With raising data density and also decreasing HDD sizes, the all at once materials demand for HDDs is not cultivation as quickly as in various other sectors, for this reason recycling older, larger-format HDDs might be able to carry out a significant fraction of the industry’s demands for newer, smaller sized ones. The fraction of the material for new HDDs that can be listed from recycling old ones might be relatively large, and it may, indeed, be feasible to make new HDDs the end of old ones because of their shrinking size.


The HDD market has some distinct features that must be thought about in creating a value-recovery system, and these can influence the use of certain technologies. The choices for value recovery native failed HDD units are presented schematically in Fig. 7.5.


The best value that have the right to be obtained from a retirement disk is achieved by repairing it and/or reusing it quite than recycling it. Tough disks space retired when they lose accessibility to a predetermined fraction of your capacity, and this can occur due to the fact that of software program errors that have the right to be corrected, permitting the unit come be returned to service, or it deserve to occur since of hardware errors that are more an overwhelming to remediate. A disk the has far-reaching unrecoverable capacity can be reformatted as a lower-capacity unit that still has actually usable life. Over there is a prospering market in recovering and selling retirement HDDs because that reuse, which provides greater worth recovery than any type of recycling process: it additionally significantly reduces the volume that HDDs that are accessible for recycling at any kind of time, which can reduce the fraction of the supply chain that can be met through recycling.

When one HDD is retired from service, it has a big amount that data that need to be protected versus unauthorized access. This may be completed by erasing the data if the disc is to be reused, and also this is part of the procedure of preparing a decaying for secondary markets, but the data top top disks eliminated from recycle units have the right to still it is in accessed, and also the assurance that data devastation is critical consideration. This results decisions around how and also where HDD recycling is done: it generates a preference for solution that physically ruin the disks from the HDDs and also for processes that are conducted at the site where the disks space retired, under the supervision of their owner.

There are clearly several technical options to be thought about with regard come recycling HDDs, and the iNEMI task will research them in detail. With regard to the most prominent critical material in one HDD, the neodymium magnet, the variety of alternatives runs from recovering the individual facets in the magnets, to recovering the magnet material, come recovering and also reusing the magnets themselves, and also eventually to recovering and reusing the magnet assemblies. Each of this calls for successively much less processing before the product is reused, and also the critical three, in particular, are attractive if the recovered materials, magnets, or magnet assemblies are used for making brand-new HDDs: this stays clear of the require to adjust the composition that is likely to be required if the magnets or materials get in other applications.

The most attractive option is probably the reuse that magnet assemblies, yet this needs stability of the HDD architecture from generation come generation, and it restricts the procedure to the supply chain the an individual manufacturer unless industry-wide magnet assembly designs deserve to be adopted. Some level of magnet assembly reuse might be possible for voice-coil motor components, yet it is rather less likely the magnet assemblies indigenous spindle motors have the right to be properly harvested, for this reason the economic viability of recycling the different types of magnets in a HDD is most likely to it is in different, and the voice-coil motor is absolutely the more attractive target.


Yasuo Cho, in Scanning Nonlinear Dielectric Microscopy, 2020

4.2.5 An difficult disk journey scanning nonlinear dielectric microscopy data storage unit for high-density ferroelectric recording

As described above, an HDD test device allowed writing and also reading at rates of 20 and also 2 Mbps, respectively <51>. Also so, this mechanism did not allow recording densities on the 1 Tbit/in.2 scale. However, subsequent work using a comparable system listed this level of storage density. In these trials, a CLT single crystal was offered as the recording tool <52>, because this medium permits the generation the the nanodomain dots required for high-density data warehouse <35,52>. A really thin ferroelectric layer is thought to be necessary when attempting come write small inverted domains while boosting the recording density. This is required due to the fact that the electrical field is concentrated automatically below the tip as soon as using a diluent film <53>. In the trial debated here, ferroelectric recording media were produced via the mechanical polishing of wafers make of single crystals, obtaining thicknesses of around 1.8 μm. The desired exact thicknesses were acquired via dry etching utilizing electron cyclotron resonance. Both the thin refined film and the substrate were written of the same material to make certain that these contents underwent the exact same level of thermal expansion. The resulting recording medium had actually a surface ar area the 15×15 mm2 and a thickness that 46±15 nm and also polarization was used to the whole medium in the bottom direction.


An SNDM image showing a 7×7 array of inverted domain dots top top the CLT tool is detailed in Fig. 4.15A. The voltage pulses used to form these dots had durations ranging from 10 come 100 ns and pulse amplitudes between 4 and 10 V. Adhering to pulse application, the medium was based on a 1 V dc offset voltage so regarding stabilize the dots. The period size exhibited a tendency to decrease with decreases in both the pulse duration and also amplitude. A enhanced image the the smallest dot (indicated by the black square in Fig. 4.15A) is presented in Fig. 4.15B, while Fig. 4.15C gift the line profile obtained from this very same dot. The period was created using a 40 ns, 5 V voltage pulse in conjunction with a 1 V balance out voltage, and also had a diameter that 12 nm. This dimension was sufficiently small such that selection having a recording density in excess of 1 Tbit/in.2 to be possible.

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A R/W test was also performed by tracing the selection after composing to create a readout signal. One SNDM image of the composed bits resulting from this trial, make by using 100 ns, 11.8 V pulses along with a 1.5 V offset and also a pulse time expectancy of 167 μs, is shown in Fig. 4.17A. This trial proved the correct writing of the bit array, with 25.8 nm spacing, same to a 0.97 Tbit/in.2 storage density. A representative real-time check out signal acquired throughout this test is presented in Fig. 4.17B. Here, the “1” and also “0” signals repeat in ~ 167 μs intervals, similar to the time span applied during the little writing process. This result indicates the the bits were accurately read. Adhering to a rapid Fourier change (see Fig. 4.17C), a signal-to-noise ratio of 3.9 dB was determined.