Regensburg 2013 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 38: Correlated Electrons: Metal-Insulator Transition 1

TT 38.1: Talk

Wednesday, March 13, 2013, 09:30–09:45, H20

Verwey Transition in epitaxial Fe₃O₄ thin films studied by Raman spectroscopy — •Mehrdad Baghaie Yazdi¹, Kwang-Yong Choi², Dirk Wulferding³, Peter Lemmens³, and Lambert Alff¹ — ¹TU Darmstadt, Materialwissenschaft — ²Chung-Ang University, Department of Physics, Seoul, Korea — ³TU Braunschweig, Institut für Festköperphysik

Magnetite has served as the model material for metal insulator transitions for more than seven decades. However, the origin and nature of the Verwey transition remains debated to this day. Recent disputes over the interpretation of measurement data [1,2] have reignited the question over the fundamental driving force behind the Verwey transition. Currently two major models try to explain the origin of this phenomenon, namely one that postulates that the transition is structurally driven [3] while the other sees the ordering of the t_2g orbitals of the Fe²⁺ ions at the octahedral sites as the main cause for both charge localization and structural transformation. Using epitaxial thin films of magnetite grown on Al₂O₃ and MgO which exhibit different Verwey transition temperatures, 128 K and 119 K respectively, we have investigated the evolution of ordering peaks in Raman spectroscopy. These peaks have been correlated to the global magnetic and electric properties of the films measured by SQUID and four-point electrical transport measurements.
[1] A. Tanaka et al., Phys. Rev. Lett. 108, 227203 (2012).

[2] S. B. Wilkins et al., Phys. Rev. B 79, 201102(R) (2009).

[3] G. Kh. Rozenberg et al., Phys. Rev. Lett. 96 045705 (2006).