Dresden 2006 – scientific programme
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MA: Magnetismus
MA 24: Magnetic Thin Films III
MA 24.7: Talk
Thursday, March 30, 2006, 11:45–12:00, HSZ 03
Antiferromagnetic centers in Fe3−δO4 magnetite films — •Ivo Knittel1, Jiandong Wei1, Michael R. Koblischka1, Yang Zhou2, Igor V. Shvets2, and Uwe Hartmann2 — 1Department of Experimental Physics, University of Saarbrücken, Saarbrücken, Germany — 2SFI Nanoscience Laboratory, School of Physics, Trinity College Dublin, Dublin 2, Ireland
Structures of magnetite (Fe3−δO4) and many other ferrites contain characteristic defects called anti-phase boundaries (APB) resulting from the symmetry mismatch between substrate and ferrite. In magnetic films containing APB, there is evidence of strong antiferromagnetic coupling across the APB. These antiferromagnetic defects essentially determine the magnetism and magnetoresistance of the films. However, direct demonstration of the magnetic frustration at the APB was not achieved so far. We report the first imaging of antiferromagnetic coupling across APB. We employed epitaxial films of Fe3O4 grown on MgO(100) substrates. By postprocessing, the magnetite films acquire a stripe domain pattern. This is indicative of a low density of magnetically active APB. As imaging tool we used a MFM in a variable magnetic field. By observing (rare) remagnetization events we demonstrate the presence of dipolar centers resulting from the APB. Magnetization reversal of isolated and interacting groups of dipolar centers is shown. The observed centers are stable up to the maximum value of the applied fields. This work is supported by the EU-funded project ’ASPRINT’.