Berlin 2012 – wissenschaftliches Programm
MA 19: Joint Session "Multiferroics III - Strain / New Routes towards Multiferroicity" (jointly with DF, DS, KR, TT)
MA 19.9: Vortrag
Dienstag, 27. März 2012, 11:45–12:00, EB 301
Relaxor ferroelectricity in pure and doped magnetite — •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
A possible example for a multiferroic material is the extensively studied magnetite Fe3O4, which shows charge-order (CO) below the Verwey transition at TV ≈ 120 K and is ferrimagnetically ordered below 500 K1. As shown in the present contribution, dielectric spectroscopy reveals a relaxation below TV, indicating relaxorlike polar order in Fe3O42. We find long-range ferroelectric order to be impeded by the continuous freezing of polar degrees of freedom and the formation of a tunneling-dominated glasslike state of electrons at low temperatures. To reveal the origin of the ferroelectric state, whose dielectric signature is partly superimposed by a so called Maxwell-Wagner (MW) relaxation, we have investigated doped samples with Al, Ga, and Mg. The dielectric spectra of these doped samples (< 2%) provide further evidence for the relaxor ferroelectric state of Fe3O4 and demonstrate the influence of the MW relaxation.
1D. I. Khomskii, J. Magn. Magn. Mater. 306, 1 (2006).
2F. Schrettle et al., Phys. Rev. B 83, 195109 (2011).