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MA: Fachverband Magnetismus

MA 11: Magnetic Heuslers, Half-metals and Oxides II (with TT)

MA 11.2: Vortrag

Montag, 31. März 2014, 15:45–16:00, BEY 118

Giant Verwey transition in magnetite thin films — Mehrdad Baghaie Yazdi and •Lambert Alff — Institut für Materialwissenschaft, TU Darmstadt

The Verwey transition in magnetite is an enigmatic challenge of solid state physics since several decades. It is generally believed that the change in magnetic moment at the Verwey transition is due to a change in magnetocrystalline anisotropy and spin reorientation. In thin films of magnetite with extraordinary high Verwey transition at 128 K, we have observed a giant change of magnetic moment above 1000%. Using several methods including neutron reflectometry we rule out spin reorientation as the origin of our observation. In addition, Raman scattering experiments show that the structural phase transition occurs at temperatures above the magnetic Verwey transition while, in contrast, newly emerging modes indicating additional charge and orbital order appear only at the Verwey transition. This result suggests that the structural phase transition in magnetite is a necessary precursor triggering a transition into a complex charge and orbitally ordered state.