Berlin 2012 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe
TT: Fachverband Tiefe Temperaturen
TT 33: Superconductivity, Measuring Devices, Matter at Low Temperature: Poster Session
TT 33.73: Poster
Mittwoch, 28. März 2012, 15:00–19:00, Poster B
Broadband dielectric spectroscopy on transition metal oxides: Is LuFe2O4 ferroelectric? — •Daniel Niermann1, Joost de Groot2, Manuel Angst2, and Joachim Hemberger1 — 1II. Physikalisches Institut, Universität zu Köln, 50937 Köln — 2Institut für Festkörperforschung, Forschungszentrum Jülich, 52425 Jülich
The mixed valence system LuFe2O4 was proposed to show a novel type of ferroelectricity based on charge order within triangular Fe-O-double layers at 330 K [1]. However, an unambiguous evidence for ferroelectricity by means of dielectric polarization measurement, e.g. hysteretical P-E-loops, is difficult to give due to the relatively high residual conductivity in this material.
We show results of temperature-dependent dielectric measurements on the potentially multiferroic material LuFe2O4 in a broad frequency range from mHz to GHz. Our measurements on a singlecrystalline sample [2] show very high magnitudes of both real and imaginary part of complex permittivity, decreasing towards low temperatures and high frequencies according to those reported in literature [1]. However in the temperature range from 200 - 400 K this dispersive behaviour is well-described by a standard equivalent-circuit model considering Maxwell-Wagner-type contacts and variable range hopping AC-conductivity, without a pronounced contribution of intrinsic dipolar polarization and thus the ferroelectric character of the charge order in LuFe2O4 has to be questioned. (Work supported by DFG through SFB 608.
[1] N. Ikeda et al., Nature 436, 1136 (2005)
[2] M. Angst et al., PRL 101 (2008), 227601