Exchange Spring Media
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Exchange spring media (also exchange coupled composite media or ECC) is a
magnetic storage Magnetic storage or magnetic recording is the storage of data on a magnetized medium. Magnetic storage uses different patterns of magnetisation in a magnetizable material to store data and is a form of non-volatile memory. The information is acc ...
technology for
hard disk drive A hard disk drive (HDD), hard disk, hard drive, or fixed disk is an electro-mechanical data storage device that stores and retrieves digital data using magnetic storage with one or more rigid rapidly rotating hard disk drive platter, pla ...
s that allows to increase the storage density in
magnetic Magnetism is the class of physical attributes that occur through a magnetic field, which allows objects to attract or repel each other. Because both electric currents and magnetic moments of elementary particles give rise to a magnetic field, m ...
recording. The idea, proposed in 2004 by Suess et al., is that the recording media consists of
exchange Exchange or exchanged may refer to: Arts, entertainment and media Film and television * Exchange (film), or ''Deep Trap'', 2015 South Korean psychological thriller * Exchanged (film), 2019 Peruvian fantasy comedy * Exchange (TV program), 2021 Sou ...
coupled soft and hard magnetic layers. Exchange spring media allows a good writability due to the write-assist nature of the soft layer. Hence, hard magnetic layers such as FePt, CoCrPt-alloys or hard magnetic multilayer structures can be written with conventional write heads. Due to the high
anisotropy Anisotropy () is the structural property of non-uniformity in different directions, as opposed to isotropy. An anisotropic object or pattern has properties that differ according to direction of measurement. For example, many materials exhibit ve ...
these grains are thermally stable even for small grain sizes. Small grain sizes are required for high density recording. The introduction of the soft layer does not decrease the thermal stability of the entire structure if the hard layer is sufficiently thick. The required thickness of the hard layer for best thermal stability is the exchange length of the hard layer material. The first experimental realization of exchange spring media was done on Co-PdSiO multilayers as the hard layer which was coupled via a PdSi interlayer to a FeSiO soft layer. Besides the improved writeability, another advantage of exchange spring media is, that the switching field distribution of the grains, which has to be as small as possible to allow for high storage densities, can be decreased. This effect was predicted theoretically and experimentally verified on Co/ Pd multilayers as hard layer coupled to Co/ Ni multilayers as soft layer. In commercial hard disks exchange spring media is used since about 2007.


See also

*
Heat-assisted magnetic recording Heat-assisted magnetic recording (HAMR) (pronounced "''hammer''") is a magnetic storage technology for greatly increasing the amount of data that can be stored on a magnetic device such as a hard disk drive by temporarily heating the disk materia ...
— Another technology to improve the writeability of high coercive materials such as FePt * Patterned media * Shingled magnetic recording


References

{{Reflist Computer storage technologies Magnetic devices