Berlin 2012 – scientific programme
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MA: Fachverband Magnetismus
MA 16: Magnetic Particles / Clusters II
MA 16.3: Talk
Tuesday, March 27, 2012, 10:00–10:15, EB 202
Magnetization reversal of individual Co nanoislands — •Safia Ouazi1, Sebastian Wedekind1, Guillemin Rodary1,2, Hirofumi Oka1, Dirk Sander1, and Jürgen Kirschner1 — 1Max-Planck-Institut für Mikrostrukturphysik, Halle (Saale), Germany — 2Laboratoire de Photonique et Nanostructures/CNRS, Marcoussis, France
We investigate the field induced magnetization reversal of individual Co islands on Cu(111) in the size range of 700 to 18000 atoms by spin-polarized scanning tunneling microscopy at 8 K. The switching field Hsw changes with island size in a non-monotonous manner: it increases with island size and reaches a maximum value of 2.4 T at 5500 atoms, and it decreases for larger islands. We extract the energy barrier for magnetization reversal as a function of island size. Our analysis reveals that the Co islands are magnetically inhomogeneous. The outer rim is magnetically soft, whereas the center region is magnetically hard. Thus, Co islands may be regarded as an exchange spring nanomagnet [1]. For larger islands, we propose that the magnetization reversal occurs by domain nucleation and growth. Our results elucidate a crossover of the magnetization reversal from an exchange spring behavior to domain wall formation with increasing size.
[1] H. Zeng, J. Li, J. Liu, Z. Wang, and S. Sun, Nature 420, 395 (2002).