Regensburg 2007 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 20: Correlated Electrons - Poster Session

TT 20.44: Poster

Mittwoch, 28. März 2007, 14:00–17:45, Poster A

Crystal growth, dielectric and magnetic investigation of 3d transition metal tungstates MWO₄ (M = Mn, Fe, Co, Ni) — •Sven Jodlauk¹, Daniel Khomskii², Petra Becker¹, Ladislav Bohatý¹, Oliver Heyer², Nils Hollmann², Harald Kierspel², Thomas Lorenz², and John Mydosh² — ¹Institut für Kristallographie, Universität zu Köln — ²II. Physikalisches Institut, Universität zu Köln

Some tungstates MWO₄ seem to be promising candidates for multiferroics whose dielectric properties are caused by a spiral spin ordering. Single-crystal growth of 3d transition metal tungstates MWO₄ (M = Mn, Fe, Co, Ni) can either be done using the flux technique and an adapted melt solvent from the system Na₂WO₄ - WO₃ (basing on early work of Schultze et al. [1]) or, especially in the case of MnWO₄, from high-temperature melt. This latter method is able to prevent Mn²⁺ from oxidation. Single crystals of MnWO₄ obtained from our crystal growth are of ruby-red color and of dimensions up to 25 * 5 * 4 mm³. Temperature dependent dielectric and pyroelectric measurements on MnWO₄ (using a (010) plate) reveal anomalies which correlate with the anomalies that were detected for temperature dependent magnetic susceptibility. This signals that MnWO₄ is a magneto-electric multiferroic. Results of this work have been published in [2].

References

[1] D. Schultze, K.-Th. Wilke, Ch. Waligora: Z. anorg. allg. Chemie 352 (1967) 184-191. [2] O. Heyer et al.: J. Phys.: Condens. Matter 18 (2006) L471-L475.