Regensburg 2016 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 36: Magnetization and Demagnetization Dynamics III

MA 36.9: Vortrag

Mittwoch, 9. März 2016, 17:15–17:30, H34

Anomalously low magnetic damping of a metallic ferromagnet Fe_1−xCo_x — Martin Schoen^1,2, •Danny Thonig³, Michael Schneider¹, Thomas Silva¹, Hans Nembach¹, Olle Eriksson³, Olof Karis³, and Justin Shaw¹ — ¹Quantum Electromagnetics Division, National Institute of Standards and Technology, USA — ²Institute of Experimental and Applied Physics, University of Regensburg, Germany — ³Department of Physics and Astronomy, University Uppsala, Sweden

Scaling of magnetic memory devices will require extremely low Gilbert damping. Ultra low damping (< 0.001), has only been found in non-metallic materials such as YIG or Heusler alloys. Recent theoretical work by Mankovsky et al. [1], however, predict damping of about 0.0007 in metallic CoFe alloys at 10% Co concentration. Such low values of the damping are highly uncommon in conducting ferromagnetic systems.

To confirm the predictions, we preformed a systematic FMR studies of the damping in Co_xFe_1−x systems spanning the full alloy composition range. Our measurements are corroborated by first principle DFT calculations of the electron structure.

We found a minimum of the damping in FeCo at 25% Co concentration, consistent with density of states calculations at 25% Co. The minimum of the damping in Co_0.25Fe_0.75 exhibits a — for conducting ferromagnets unprecedented — low value of α= 0.0005, showing the practicality of metal alloys for spintronics.

[1] Mankovsky et al., Phys. Rev. B 87, 014430 (2013)