Toward single-atom memory

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Science  15 Apr 2016:
Vol. 352, Issue 6283, pp. 296-297
DOI: 10.1126/science.aaf2481

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Storing information in an ensemble of single-atom magnets represents the ultimate miniaturization of data storage technology, in which two specific orientations of each atomic magnetic moment represent a bit (a 0 or 1) of information (see the figure, panel A). The inherent dilemma in using a single-atom magnet is keeping it magnetized—or, in other words, being able to hold the information in one of the bit states without an external magnetic field for a useful amount of time and at practical temperatures (1, 2). This phenomenon of magnetic remanence is dif cult to realize from a single atom, in part because diminished robustness against fluctuations from the environment can unintentionally flip the magnetic state, thus wiping out the magnetic memory. A recent attempt to observe remanence in a single atom (3) proved premature, as the results were incompatible with the magnetic ground state of that system (4) and could not be reproduced (4, 5). Hence, the question of whether this defining property of a single-atom magnet can actually be achieved has remained an open question until now. On page 318 of this issue, Donati et al. (6) demonstrate that single holmium atoms exhibit magnetic remanence up to temperatures of 40 K, much higher than previous records of atomic-scale magnets composed of 3 to 12 atoms (1, 2, 5)—a record in both size and stability for any magnet.