Regensburg 2013 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 16: Poster I

MA 16.2: Poster

Dienstag, 12. März 2013, 10:30–13:30, Poster D

Magnetic and dielectric properties of doped magnetite - multiferroicity? — •Eugen Ruff¹, Florian Schrettle¹, Stephan Krohns¹, Peter Lunkenheimer¹, Victor A.M. Brabers², and Alois Loidl¹ — ¹Experimental Physics V, University of Augsburg, 86135 Augsburg, Germany — ²Department of Physics, Eindhoven University of Technology, 5600 MB Eindhoven, Netherlands

We investigate pure and Al-doped magnetite (single-crystals) using magnetometry, specific heat measurements, and broadband dielectric spectroscopy to analyze the magnetic properties at the Verwey transition and to check for its ferroelectric properties. At low magnetic fields the magnetic moment of magnetite shows an interesting anomaly at the Verwey transition. One can speculate, that this is due to magnetic softening, which is verified by magnetization measurements around the Verwey temperature. For an Al-content x<0.3 (Fe_3−xAl_xO₄) the anomaly shifts to lower temperatures with increasing x and for x≥0.03 it is suppressed. The results of dielectric spectroscopy and specific heat measurements confirm this behavior. At low temperatures, the dielectric properties of the low doped samples are consistent with relaxor ferroelectricity as evidenced by Schrettle et al. [PRB 83, 195109 (2011)] for the undoped material. We found the detected relaxorlike peak to be strongly influenced by doping. The analysis of the temperature dependent relaxation time reveals a freezing of polar dynamics, which becomes faster with higher doping level.