Structure and geometrically frustrated magnetism of layered oxide-cluster compounds

Datum

07.07.2017

Zeit

13:00 - 14:00

Sprecher

Prof. Tilo Söhnel

Zugehörigkeit

School of Chemical Sciences, University of Auckland, New Zealand

Sprache

en

Hauptthema

Materialien

Andere Themen

Materialien, Physik

Host

Christine Malbrich

Beschreibung

Layered oxides containing third row transition metals possess interesting crystal and electronic architectures, which may exhibit novel multiferroic properties such as ferroelectricity and giant magnetoresistance.[1] The parent compound for this presentation Fe4Si2Sn7O16 can be described as a layered composite of intermetallic (FeSn6) clusters and perfect kagomé lattice type (FeO6)/(SnO6) oxide layers within the one structure.[2] SiO4 tetrahedra separate these layers which leads to electronic and magnetic isolation of the repeated layers by about 7 Å resulting in a nearly perfectly 2D oxide system comparable to a one layer thick oxide “thin film”. This combination of features therefore allows us a unique opportunity to study the electronic interaction of two materially independent features in the one material. In this study we have replaced iron positions with cobalt and/or manganese [3] in order to study the change in structure and material properties. Refinements of the structures based on synchrotron and neutron diffraction data show the distinct different behaviour of Mn and Co replacement in MSn6 octahedral layer in these materials. Compounds containing both iron and cobalt may result in the first 19-electron cluster seen in these tin systems. The resulting electronic structure will be discussed based on DFT calculations and XANES measurements. 57Fe-Mössbauer spectra confirm the observation from neutron diffraction studies and show that Mn has a strong affinity for the oxide layer positions, whereas Co preferably occupies the of intermetallic Sn cluster layer. The Fe/Mn cluster compounds show an antiferromagnetic ordering below 3 K. The magnetically frustrated structures could be solved using low temperature neutron powder diffraction data [4]. [1] Cheong, S.W. and Mostovoy, M. Nature Mater. 2007, 6, 13. [2] Söhnel, T., Böttcher, P., Reichelt, W. and Wagner, F. E. Z. Anorg. Allg. Chem. 1998, 624, 708. [3] Allison, M.C., Avdeev, M., Schmid, S., Liu, S., Söhnel, T. and Ling, C.D. Dalton Trans. 2016, 45, 9689-9694. [4] Ling C. D., Allison M. C. , Schmid S. A., Adveev M., J. S. Gardner J. S., Wang C.-W., Stewart G. A., Ryan D. H., Söhnel T. 2017. arXiv:1703.08637; Phys. Rev. Letters, submitted.

Links

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Letztmalig verändert: 07.07.2017, 09:36:02