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Magnets too slow for disk writes? Use lasers

PSI scientists demo picosecond magnetic 'write'

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A group of Swiss researchers has demonstrated using lasers to control magnetisation at extremely high speed, a line of research they hope will one day will help speed up hard drives.

One of the limits of the modern hard drives' performance is how quickly a bit's magnetisation can be accurately changed using a magnetic write mechanism.

The researchers at the Paul Scherrer Institute are trying a different angle. Instead of using a magnet for the read-write activity, they've used a laser instead. The terahertz instrument the institute developed for its experiment was able to control the magnetisation of their target material at picosecond timescales.

Published at Nature (abstract here), the group says it has achieved “coherent, phase-locked between a high-field single-cycle terahertz transient and the magnetisation of ferromagnetic cobalt films”.

Getting the magnetic moments – that is, magnetised particles on the ferromagnetic surface – to change state in a picosecond is one trick. Doing so reliably is a second challenge, and for this, the researchers say in this release, they developed a laser with high phase stability.

The PSI researchers haven't yet achieved a complete flip from a 1 state to a 0 state using the laser. The current experiment was, however, enough to let them observe the movement of the magnetic moments. However, according to Christoph Hauri, head of the laser group and professor at Switzerland's EPFL, the group is confident that the beams can be enhanced enough to switch the magnetisation of bits. ®

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