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MA: Fachverband Magnetismus
MA 46: Magnetic Thin Films I
MA 46.5: Vortrag
Donnerstag, 19. März 2015, 16:00–16:15, H 1012
Increased magnetic moment induced by lattice expansion from α-Fe to α′-Fe8N — Imants Dirba1, Philipp Komissinskiy1, Dominik Gölden1, Oliver Gutfleisch1,2, and •Lambert Alff1 — 1Institute of Materials Science, Technische Universität Darmstadt, 64287 Darmstadt — 2Fraunhofer-Projektgruppe für Wertstoffkreisläufe und Ressourcenstrategie IWKS, 63457 Hanau
We have grown buffer-free and epitaxial α-Fe and α′-Fe8Nx thin films by RF magnetron sputtering and molecular beam epitaxy onto MgO (100) substrates. The film thicknesses and densities have been determined with high accuracy by evaluating the Kiessig fringes of X-ray reflectometry measurements allowing a precise volume estimation. A gradual increase of the nitrogen content in the plasma led to an expansion of the iron bcc unit cell along the [001] direction resulting finally in a tetragonal distortion of about 10% corresponding to the formation of α′-Fe8N. The α-Fe lattice expansion was accompanied by an increase in magnetic moment to 2.61±0.06 µB per Fe atom, and an increase in anisotropy of around 6000 Oe. Our experiments show that - without requiring any additional ordering of the nitrogen atoms - the lattice expansion of α-Fe itself is the origin of the increased magnetic moment in α′-Fe8N.