Reaching the molecular limit of magnetic memory

This year we are likely to see the first ‘exascale’ computer – able to carry out at least 10¹⁸ operations per second. The computer itself will be the size of 10 tennis courts, but it will require the smallest electronic components possible. IBM, for example, have just announced their latest chip will have 333 million transistors per square millimetre - that’s a footprint of 2nm for each transistor. The size of the other crucial part of computer technology, magnetic memory, is not shrinking at the same rate, however. The current state of the art technology will store a single bit of data in a dozen or so magnetic grains, each around 3nm. Memory is becoming the weakest link in the race to faster and more powerful computing.

Enter chemistry and the single molecule magnet. Could the current solid magnetic grains be replaced by a single molecule less than 1nm across , whose magnetic state could be imprinted with binary data? Until the last few years this seemed clearly in the realms of science fiction, but in 2017 two groups published ground-breaking results, showing that a single dysprosium complex could be magnetised and remain in that state at up to 60K. Although that temperature threshold is very cold, it can be reached using liquid nitrogen, rather than colder temperatures which require expensive liquid helium cooling. This is only one small step along the road to molecular-scale magnetic memory, but some research groups across chemistry and physics are starting to think seriously about how it might be done.