Industrial - Hard Disks - PMM

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Hard Disks

Pgm and data storage

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The amount of data requiring digital storage continues to grow at a fantastic rate. No longer confined to use in computers, hard disk drives can now be found in televisions, games consoles and other home entertainment systems as a store of non-volatile data. The amount of platinum and ruthenium has increased rapidly over the years as storage densities have increased to meet demand. The first hard disk drive, introduced in 1957, used fifty disks, each measuring 24 inches in diameter, to store just 5 megabytes of data. Today hard disk drives are available which can store upwards of 3 terabytes.

Inside a hard disk drive

A hard disk drive operates using several of the same principles as an old fashioned record player. Information is recorded and retrieved by a magnetic head mounted on a moveable arm, which moves over a rapidly spinning disk (also called a platter). Each drive contains one or more platters, made of highly polished aluminium or glass, stacked together with one read/write head per side of each disk.

The platters are produced by depositing several very thin layers of materials to provide the required smoothness, magnetic storage capability and lubrication. The first pgm containing layer is the "soft magnetic underlayer". This layer is unique to the current perpendicular magnetic recording (PMR) disks and is needed to enhance the perpendicular field needed to write the data. This typically consists of two Co-Ni-Fe layers separated by a 4 atom thick layer of ruthenium. The magnetic storage layer consists of a Co-Cr-Pt alloy composing several sub layers. The cobalt provides the necessary orientation of the crystals; the chromium improves the signal-to-noise ratio, while the platinum provides thermal stability. Ruthenium is also to be found here, although performing a somewhat different role than in the soft underlayer. Its role is to help orientate the magnetic grains, as well as reducing interference between layers.

The vital roles played by both ruthenium and platinum have enabled hard disk manufacturers to produce massive leaps in storage density and they will continue to play a role in the next generation of hard disk drives and the new technology that uses them.