Pixie Dust

This IT Engineering Seminar Topic deals with the following:

In each of the past five years, hard drive capacities have doubled, keeping storage costs low and allowing technophiles and PC users to sock away more data. However, storage buffs believed the rate of growth could continue for only so long, and many asserted that the storage industry was about to hit the physical limit for higher capacities. But according to IBM, a new innovation will push back that limit. The company is first to mass produce computer hard disk drives using a revolutionary new type of magnetic coating that is eventually expected to quadruple the data density of current hard disk drive products — a level previously thought to be impossible, but crucial to continue feeding the information-hungry Internet economy. For consumers, increased data density will help hasten the transition in home entertainment from passive analog technologies to interactive digital formats.

The key to IBM’s new data storage breakthrough is a threeatom-thick layer of the element ruthenium, a precious metal similar to platinum, sandwiched between two magnetic layers. That only a few atoms could have such a dramatic impact caused some IBM scientists to refer to the ruthenium layer informally as “pixie dust”. Known technically as “antiferromagnetically-coupled (AFC) media,” the new multilayer coating is expected to permit hard disk drives to store 100 billion bits (gigabits) of data per square inch of disk area by 2003. Current hard drives can store 20 gigabits of data per square inch. IBM began shipping Travelstar hard drives in May 2001 that are capable of storing 25.7 gigabits per square inch. Drives shipped later in the year are expected to be capable of 33% greater density.

In information technology, the term “pixie dust” is often used to refer to a technology that seemingly does the impossible. In the past decade, the data density for magnetic hard disk drives has increased at a phenomenal pace: doubling every 18 months and, since 1997, doubling every year, which is much faster than the vaunted Moore’s Law for integrated circuits. It was assumed in the storage industry that the upper limit would soon be reached. The superparamagnetic effect has long been predicted to appear when densities reached 20 to 40 gigabits per square inch – close to the data density of current products.

IBM discovered a means of adding AFC to their standard production methods so that the increased capacity costs little or nothing. The company, which plans to implement the process across their entire line of products, chose not to publicize the technology in advance. Many companies have focused research on the use of AFC in hard drives; a number of vendors, such as Seagate Technology and Fujitsu, are expected to follow IBM’s lead.

AFC will be used across all IBM hard drive product lines. Prices of hard drives are unlikely to increase dramatically because AFC increases the density and storage capacity without the addition of expensive disks, where data is stored, or of heads, which read data off the disks. AFC will also allow smaller drives to store more data and use less power, which could lead to smaller and quieter devices.

Developed by IBM Research, this new magnetic media uses multilayer interactions and is expected to permit longitudinal recording to achieve a future data density of 100 gigabits/inch2 without suffering from the projected data loss due to thermal instabilities. This new media will thus delay for several years the impact of super paramagnetism in limiting future areal density increases. It also requires few changes to other aspects of the hard-disk-drive design, and will surely push back in time the industry’s consideration of more complex techniques proposed for very high-density magnetic recording, such as, perpendicular recording, patterned media or thermally-assisted writing.

Read-Rite’s recording heads are the miniaturized hearts of disk drives and other magnetic storage devices. While they may appear to be simple components, their design and manufacture require leading-edge capabilities in device modeling, materials science, photolithography, vacuum deposition processes, ion beam etching, reliability testing, mechanical design, machining, air bearing design, tribology, and other critical skills. In general, recording heads function according to certain principles of magnetic recording which are based directly on four magnetic phenomena:

Writing Magnetic Data
Simplified sketches of a writing head are shown in Figure1. The view from the top of the writing head (left) shows a spiral coil wrapped between two layers of soft magnetic material; on the right is a cross-section of this head as viewed from the side. Note two things in this figure: at the lower end, there is a gap between these layers, and at their upper end these layers are joined together. The top and bottom layers of magnetic material are readily magnetized when an electric current flows in the spiral coil, so these layers become North and South magnetic poles of a tiny electromagnet. [In a real head, the distance from the gap to the top of the coil is about 30 microns (or 0.0012 inch).]

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