Reaching the magnetic anisotropy limit of a 3d metal atom

Ileana G. Rau, Susanne Baumann, Stefano Rusponi, Fabio Donati, Sebastian Stepanow, Luca Gragnaniello, Jan Dreiser, Cinthia Piamonteze, Frithjof Nolting, Shruba Gangopadhyay, Oliver R. Albertini, Roger M. Macfarlane, Christopher P. Lutz, Barbara A. Jones, Pietro Gambardella, Andreas J. Heinrich, Harald Brune

Research output: Contribution to journalArticlepeer-review

292 Scopus citations


Designing systems with large magnetic anisotropy is critical to realize nanoscopic magnets. Thus far, the magnetic anisotropy energy per atom in single-molecule magnets and ferromagnetic films remains typically one to two orders of magnitude below the theoretical limit imposed by the atomic spin-orbit interaction. We realized the maximum magnetic anisotropy for a 3d transition metal atom by coordinating a single Co atom to the O site of an MgO(100) surface. Scanning tunneling spectroscopy reveals a record-high zero-field splitting of 58 millielectron volts as well as slow relaxation of the Co atom's magnetization. This striking behavior originates from the dominating axial ligand field at the O adsorption site, which leads to out-of-plane uniaxial anisotropy while preserving the gas-phase orbital moment of Co, as observed with x-ray magnetic circular dichroism.

Original languageEnglish
Pages (from-to)988-992
Number of pages5
Issue number6187
StatePublished - 2014


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