19 July 2012
In a major step forward for nanoscale computing, German and Japanese researchers have created magnetic memory with one bit per molecule.
That compares with current hard disks where one bit of digital information consists of around three million magnetic molecules.
The researchers’ device consists of a single magnetic iron atom — which can be switched with an electric pulse — in the centre of an organic shell that protects the information stored within.
‘Not only does the resistance change but also the magnetic state, so it is, if you like, a combination of memristor features and spintronic features, and that’s basically the new thing,’ Prof Wulf Wulfhekel of Karlsruhe Institute of Technology (KIT) told The Engineer.
In memory resistors, or ‘memristor’ devices, resistance changes depending on how much current has passed through it and information is retained even after the power is off.
They need just a thousandth of the energy and are around 100 times faster than standard flash memory chips.
‘Memristors usually require a structural change in the material that has some disadvantage because there might be fatigue. With a metal, you switch between an amorphous high-resistance state and crystalline low-resistance state, so you crystallise, de-crystallise, crystallise and so on, so there’s diffusion,’ Wulfhekel said. ‘In our case, there’s no diffusion — this can be repeated as many times as you want; there’s no fatigue.’
Meanwhile, the magnetic aspect of the device could have interesting applications because the field of spintronics uses the magnetic spin of individual atoms for informational processing — computational power essentially.
Wulfhekel also said the manufacturing techniques for the very smallest-scale computing devices were also reaching a limit — something their method addresses.
‘The general problem with nanostructures is that, if you shrink the structure by lithography, a top-down approach, you can’t reproduce the structure exactly. Every device will be different because one has one more atom, and in another the position of the atoms is different. With molecules, chemistry does the job for you — all the molecules are identical.’