Regensburg 2010 – wissenschaftliches Programm
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KR: Fachverband Kristallographie
KR 10: Poster: Multiferroics (with MA, DF, KR, DS)
KR 10.22: Poster
Dienstag, 23. März 2010, 10:45–13:45, Poster A
Investigation of the triangular multiferroic order in CuCrO2 by second harmonic generation — •Vera Carolus1, Kenta Kimura2, Tsuyoshi Kimura2, and Manfred Fiebig1 — 1Helmholtz-Institut für Strahlen- und Kernphysik, Nußallee 14-16, D-53115 Bonn — 2Devision of Materials Physics, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan
CuCrO2 (space group R3m) is a triangular lattice antiferromagnet with delafossite structure showing a modulated out-of-plane 120∘ spin order below TN = 23.6 K. Because of the breaking of inversion symmetry by the magnetic order a magnetically induced electric polarisation with six different domains should exist.
Here we investigate the multiferroic order of CuCrO2 by optical second-harmonic generation (SHG) spectroscopy. Although the value of spontaneous polarisation is about four orders of magnitude weaker than in a conventional ferroelectric, a clear SHG signal with a pronounced spectral and polarization dependence is obtained. This giant coupling to the SHG progress is not restricted to CuCrO2, but is also observed in MnWO4, TbMn2O5 and CuO. This points to electronic instead of ionic nature of the ferroelectric polarisation.
In SHG imaging experiments the topology of the multiferroic domains (and their manipulation) were investigated. Crystallographic and magnetic correlations between the six types of domains were revealed.