Avalanche warning for your hard drive

An article has appeared on the American Physical Society website concerning the spin precession of magnetic material. When a hard drive is written to the data is stored as a series of zeroes and ones, which is indicated by the polarity of an area of the drive’s magnetic surface, i.e. the area is either postively or negatively charged. To change the polarity and thus the data bit then the spin direction of the atoms in the magnetic area is changed. It was believed that this change in direction was straight-forward and almost instantaneous during a write process.

However a bofffin at the University of California, Joshua Deutsch, along with Andreas Berger of Hitachi have published the article on the APS website that suggests that the change in rotational direction of the atoms is not as straightforward as first believed. The guys have found that the atoms undergo spin precession for a few nanoseconds as they change direction. In densely packed magnetic surfaces this could cause an ‘avanlache’ effect where neighbouring atoms change their rotational direction as well. Thus the neighbouring data bits becomes corrupted as the magnetic areas around have their polarity changed due to this spin precession.

Fortunately in current hard drives a damping effect occurs which generally prevents this corruption from occurring. However as drive spin speeds increase (another factor in causing atom spin precession) and the magnetic areas become smaller to increase drive capacity the ‘avalanche’ effect will become more of a problem. It’s not all doom and gloom for drive manufacturers as Deutsch and Berger suggest that improving the magnetic surface of drives would increase the damping effect and therefore offset the negative influences.

On that note, Western Digtal have just announced the latest addition to their MyBook hard drive range, a ‘huge’ 2TB external storage unit to be priced at around US$750.

Source: ComputerWorld