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MA: Fachverband Magnetismus

MA 51: Magnetic Half-metals and Oxides II

MA 51.9: Talk

Thursday, March 17, 2011, 13:00–13:15, HSZ 401

A study of the Verwey transition in epitaxial magnetite thin films by Raman spectroscopy and SQUID-magnetometry — •Mehrdad Baghaie Yazdi¹, Dirk Wulferding², Choi Kwang Yong^2,3, Peter Lemmens², and Lambert Alff¹ — ¹Technische Universität Darmstadt — ²Technische Universität Braunschweig — ³Chung-Ang University, Seoul, Korea

The origin of the Verwey transition, despite decades of research, remains a heavily debated fundamental property of magnetite. Its understanding involves concepts such as charge ordering which are essential in transition metal oxides. For this work, epitaxial thin films of magnetite (Fe₃O₄) have been grown, using reactive rf-magnetron sputtering, on single crystal (100) MgO (magnesium oxide) and c-cut Al₂O₃ (sapphire) substrates. The phase purity and orientation was analyzed using high resolution X-ray diffraction. The Verwey transition was studied by both Raman spectroscopy and SQUID-magnetometry. The Raman spectra of the magnetite grown on Al₂O₃ show an earlier onset of the transition at around 150 K with a definite change at T_V = 130 K, which corresponds to the data obtained by SQUID. As for the films grown on MgO, the transition is close to the literature value of 120 K.