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Berlin 2008 – scientific programme

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MA: Fachverband Magnetismus

MA 20: Multiferroics

MA 20.7: Talk

Wednesday, February 27, 2008, 15:30–15:45, EB 202

Characterization of multiferroic HoMnO3 films by second harmonic generation — •Tobias Kordel1, Christian Wehrenfennig1, Dennis Meier1, Thomas Lottermoser1, Catherine Dubourdieu2, Isabelle Gelard2, Kathrin Dörr3, Jong-Woo Kim3, and Manfred Fiebig11HISKP, Universität Bonn, Germany — 2LMPG, Grenoble, France — 3IFW, Dresden, Germany

The magnetic and electric properties of hexagonal HoMnO3 films were investigated by optical second harmonic generation (SHG). Symmetry arguments relate different polarized SH contributions uniquely to either the electric or magnetic properties of HoMnO3.

Epitaxial hexagonal HoMnO3 and YMnO3 films with 50-1000nm thickness were grown by PLD and MOCVD on YSZ(111) substrates. The "nonmagnetic" SHG signal in the films is similar to that of bulk HoMnO3 pointing to the presence of ferroelectric ordering. However, a "magnetic" SHG signal has not been observed. At present, this can be explained by two models: (i) The film has anitferromagnetic domains with lateral dimensions much smaller than the wavelength of the light, so that the magnetic signal cancels out by interference; (ii) the film is in a ferroelectric single domain state. This induces ferromagnetic ordering of the Ho3+ spins and a Mn3+ spin configuration for which no SHG signal is observable. The latter model is supported by the observation of misaligned crystallites in the film with a preferred direction of polarisation.

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