Regensburg 2010 – scientific programme
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MA: Fachverband Magnetismus
MA 9: Magnetic Particles, Clusters
MA 9.10: Talk
Monday, March 22, 2010, 17:45–18:00, H23
Magnetic Properties of Fe and Co Clusters on Aluminum Oxide on Ni3Al(111) — •Andreas Buchsbaum1, Pardeep Kumar Thakur2, Alexei Preobrajenski3, Edvin Lundgren4, Michael Schmid1, and Peter Varga1 — 1Institut für Angewandte Physik, Technische Universität Wien, Austria — 2ID08, ESRF, Grenoble, France — 3MAX-lab, Lund — 4Division of Synchrotron Radiation Research, Lund University, Sweden
The structure of the aluminum oxide on Ni3Al(111) with a (√67 × √67)R12.2 ∘ unit cell can be used to grow well ordered arrays of Fe and Co clusters [1]. The size of these clusters can range from 1 up to ≈1000 atoms before reaching the limit of coalescence. We have investigated the magnetic properties of Fe clusters (≈900 atoms/cluster) and Co clusters (≈500 atoms/cluster) using x-ray magnetic circular dichroism (XMCD), assisted by scanning tunnelling microscopy (STM). This technique allowed us to measure the orbital and spin contribution to the magnetic moment per Fe or Co atom, as well as hysteresis curves down to temperatures of 7 K and up to fields of 5 T. From fitting the hysteresis curves we found clusters with a tilted easy axis in both cases and contributions of different cluster species in accordance to STM. Co clusters are superparamagnetic down to 7 K and Fe clusters are ferromagnetic below ≈50 K. The anisotropy energy is slightly higher than for bulk Fe or Co.
[1] M. Schmid, et.al., Phys. Rev. Lett. 99, 196104 (2007).