Hitting the limit of magnetic anisotropy

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Science  30 May 2014:
Vol. 344, Issue 6187, pp. 976-977
DOI: 10.1126/science.1254402

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Single magnetic atoms adsorbed on surfaces, or so-called adatoms, provide a viable ground for realizing information storage and processing at ultimate length scales (13). Such concepts hinge on the magnetic anisotropy energy (MAE), which energetically favors a preferential spatial orientation of the adatom's magnetic moment m, where m is the sum of coupled spin and orbital momenta. Unlike for a free atom, where m can rotate freely in any direction without energy cost (see the figure, panel A, MAE = 0), large MAE (panel B, MAE ≠ 0) enables m to maintain a fixed orientation for a sufficient amount of time. For stable and robust magnetic memory storage, large values of MAE are desirable. On page 988 of this issue, Rau et al. (4) show that a suitable choice of substrate and adatom pairing can result in the further enhancement of MAE, thus providing a possible route toward realizing information storage at the atomic scale.