French boffins have discovered properties in the Prussian blue compound that could allow the pigment to be used in super-fast transistor switches in next-generation data storage devices.
Researchers from the Institute of Molecular Chemistry and Materials at Orsay and the Laboratory of Inorganic Chemistry and Molecular Materials showed that, while the compound is not magnetic at the outset, it can become magnetised by the effect of light and returned to its initial state by heating.
By replacing some of the Prussian blue atoms or iron with cobalt, they can transform the pigment into a compound that can act as a switch.
Illuminated by a red light at low temperature (-150°C), the compound shifts from a non-magnetic state (OFF) to a magnetic state (ON) in a way that is stable over time. If it is heated, it returns to the OFF state.
This change of state is due to the transfer of an electron from the cobalt to the iron (and vice versa) by absorption of light or thermal energy.
The researchers pointed out that the first hard disk, the RAMAC built by IBM in 1954, weighed one ton and stored five megabytes.
In today's portable computers and MP3 readers, the hard disks store several gigabytes and weigh only a few hundred or even a few dozen grams.
To miniaturise these devices further the chemists hope that the Prussian blue switches will allow them to store information on the scale of a few atoms.