IBM has been in the lead in its research labs in exploring ways to manipulate atoms (in 1989 they managed to write their name by moving single atoms of xenon) and now they have announced the capability to change the magnetic orientation of a single atom of holmium, a rare element.
The feat has been made possibile by using an electric pulse directed to the atom by the tip of a scanning tunnelling microscope (STM). They also showed the possibility to read the magnetic field orientation of a single atom.
Now, in theory this means that we can use a single atom to store a bit, associating 0 to one orientation of the magnetic field and 1 to the other, since we can set the orientation (write the bit) and sense the orientation (read). Imagine: using just one atom to store a bit, whilst today we use many thousands of atoms (100,000 in magnetic disc). This means, still in theory, that we can increase storage density by a factor of 1,000 (and more).
However, this is "in theory". The amount of atoms needed to influence and read the magnetic field is staggering and the whole procedure is cumbersome (slow and difficult to execute). We knew that it would be possible in principle to store a bit on a single atom (as we know that it is possible, in principle, to store a bit on a single electron), now we have the demonstration that this is feasible with tools we have.
Do not imagine, however, that this kind of approach can be applied for everyday storage of bits, although the demonstration may lead to further refinement that eventually might result in a practical application. We are still in the domain of pure research, quite far from industrial applications. But that is the way progress start...