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 Fiebig¹ — ¹HISKP, 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.