Dresden 2014 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 55: Poster II
MA 55.61: Poster
Freitag, 4. April 2014, 10:30–13:30, P2
Cubic magnetocrystalline anisotropies in ultrathin epitaxial magnetite films on MgO(001) — •Andreas Krampf1, Nico Pathé1, Tobias Schemme1, Timo Kuschel2, and Joachim Wollschläger1 — 1Department of Physiys, Osnabrück University, Germany — 2Department of Physics, Bielefeld University, Germany
Ultrathin films of magnetite (Fe3O4, thickness 10 nm−100 nm) are deposited on lattice matched MgO(001) substrates either by reactive molecular beam epitaxy (RMBE, Fe evaporation in molecular oxygen atmosphere) or by oxidation of previously deposited ultrathin epitaxial Fe films. Both the structure and stoichiometry of the films have been controlled by surface sensitive and bulk sensitive techniques while magnetic properties are characterized by MOKE. In both cases, the magnetite films show in-plane magnetization due to the shape anisotropy. In addition, the easy axes point in Fe3O4<110> directions as determined from the coercive fields for different crystallographic directions. This result is in agreement with the well-known easy axes <111> of bulk magnetite if projected on the planar magnetite film.
Alternatively, magnetite films are formed via a two-step growth process. First, Fe films are epitaxially grown. Thereafter, Fe3O4 has been deposited by RMBE. The result of this procedure is that the Fe film is completely consumed during growth of the additional magnetite film. The entire film has Fe3O4 structure. Surprisingly, the coercive fields are drastically enhanced and the easy axes are rotated by 45∘ so that they point into Fe3O4<100> directions. The mechanism of this effect is still under discussion.