Berlin 2015 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 2: Surface Magnetism and Spin Phenomena

O 2.1: Hauptvortrag

Montag, 16. März 2015, 10:30–11:00, MA 004

Unusual magnetic properties of Fe and Co atoms on MgO — •Andreas Heinrich — IBM Research, San Jose, USA

The ability to control the magnetic properties of nanoscale systems will open novel avenues for spintronics, magnetic memory devices, and quantum computation. Key among those properties is the magnetic anisotropy, which governs the stability and directionality of their magnetization.

I will present scanning tunneling and x-ray absorption spectroscopy measurements of Co and Fe atoms deposited on thin MgO layers. Both species retain most of their free atom orbital moment and interact strongly with the crystal field of their binding site. In the case of Co, the almost cylindrical symmetry of the binding site preserves the full orbital angular momentum around the surface normal and leads to the maximum magnetic anisotropy for 3d transition metal atoms. On the other hand, Fe responds to the four-fold perturbation of the binding site and hence has much smaller magnetic anisotropy.

Spin-polarized tunneling measurements reveal relatively stable magnetic ground states for Fe and Co with long spin relaxation times (ms range) for the excited state with opposite magnetic moment.

These results offer a strategy, based on symmetry arguments and careful tailoring of the interaction with the environment, for the rational design of nanoscopic permanent magnets and single atom magnets.