There’s a post on Technology Review’s blog about a paper on arXiv about a theoretical result in magnetic memories.

Current-day magnetic memory is already “nanotechnology” under the loose definition, involving 5-nanometer particles of cobalt (having about 50,000 atoms). The authors have shown that a single molecule consisting of a cobalt dimer sitting on top of a benzene ring would have a high enough magnetic anisotropy to store a bit magnetically.

(surprisingly enough, the cobalts prefer to stack up rather than so lie down flat on the carbon ring.)

Don’t expect this in your computer any time soon; the authors write:

Technological use would require to solve at least three additional
problems: fabrication of large regular arrays; protection against oxidation without reducing
the anisotropy; new read/write technologies. Let us finally discuss a possible method to
solve the latter problem. Conventional write technology makes use of magnetic fields B in
the order of 1 T, Ref. 2. It would fail in the present situation, where a field B = MAE/µs of
several hundred tesla would be needed.

But they then go on to show that the bit could be written (reading is relatively easy) by a scanning-probe like tip which briefly ionized the upper cobalt. The mechanisms to do that would of course still have to be designed and built; but this is exploratory engineering in atomically-precise mechanisms, and we’d like to see more of it.