Metastable Crystalline Cobalt Iron Oxide Nano‐Flakes with Antiferromagnetic/Ferrimagnetic Composition Mosaicity
Abstract
Abstract By thermal decomposition of a crystalline hydroxycarbonate precursor with a Co:Fe ratio of 2:1, crystals with alternating ferrimagnetic and antiferromagnetic nano‐domains were synthesized using a facile synthetic approach that combined bottom‐up co‐precipitation of the precursor with a self‐assembled top‐down nano‐structuring during spinel formation. Due to the miscibility gap of the spinel phase diagram at this composition, a topotactic segregation into CoFe 2 O 4 ‐like and Co 3 O 4 ‐like domains takes place at 400 °C, giving rise to porous crystalline nano‐flakes with spatial compositional fluctuations on a scale of approximately 5 nm. Experimental methods and density functional theory showed that the metastable nature of this interface‐rich material is manifested in the unexpectedly low lattice parameter of the iron‐rich domains, which can be explained by the compressive strain executed on this phase due to mosaicity. Investigations of the magnetic properties revealed an exchange bias effect, due to this unique microstructure, which is typically known for thin films or core/shell nanoparticles. Treatment at temperatures higher than 450 °C causes this microstructure to break down, the lattice strain to relax, and finally leads to properties expected for the thermodynamically stable phases according to the phase diagram.
Article Details
Authors (23)
Anna Rabe
Faculty of Chemistry University of Duisburg‐Essen Universitätsstr. 7 45141 Essen Germany
Franz‐Philipp Schmidt
Department of Inorganic Chemistry Fritz Haber Institute of the Max Planck Society 14195 Berlin Germany
Shohreh Rafiezadeh
Faculty of Physics University of Duisburg‐Essen and Center for Nanointegration Duisburg‐Essen (CENIDE) Lotharstr. 1 47057 Duisburg Germany
Soma Salamon
Faculty of Physics University of Duisburg‐Essen and Center for Nanointegration Duisburg‐Essen (CENIDE) Lotharstr. 1 47057 Duisburg Germany
Joachim Landers
Faculty of Physics University of Duisburg‐Essen and Center for Nanointegration Duisburg‐Essen (CENIDE) Lotharstr. 1 47057 Duisburg Germany
Mirco Eckhardt
Department of Chemistry University of Bayreuth Universitätsstr. 30 95440 Bayreuth Germany
Christoph Pratsch
Department of X‐ray Microscopy Helmholtz‐Zentrum Berlin für Materialien und Energie GmbH Albert‐Einstein‐Str. 15 12489 Berlin Germany
Benedikt Beckmann
Institute of Materials Science Technische Universität Darmstadt 64287 Darmstadt Germany
Felix Thomas Haase
Department of Interface Science Fritz Haber Institute of the Max Planck Society Faradayweg 4‐6 14195 Berlin Germany
David Kordus
Department of Interface Science Fritz Haber Institute of the Max Planck Society Faradayweg 4‐6 14195 Berlin Germany
Mauricio Lopez Luna
Chemical Sciences Division
Clara Rettenmaier
Department of Interface Science Fritz Haber Institute of the Max Planck Society Faradayweg 4‐6 14195 Berlin Germany
Thomas Götsch
Department of Inorganic Chemistry Fritz Haber Institute of the Max Planck Society 14195 Berlin Germany
Axel Knop‐Gericke
Department of Inorganic Chemistry Fritz Haber Institute of the Max Planck Society 14195 Berlin Germany
Arno Bergmann
Janis Timoshenko
Department of Interface Science, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, Berlin 14195, Germany
Beatriz Roldan Cuenya
Department of Interface Science
Oliver Gutfleisch
Mirijam Zobel
Institute of Crystallography, RWTH Aachen University, Jägerstr. 17-19, 52066 Aachen, Germany
Rossitza Pentcheva
Faculty of Physics University of Duisburg‐Essen and Center for Nanointegration Duisburg‐Essen (CENIDE) Lotharstr. 1 47057 Duisburg Germany
Heiko Wende
Faculty of Physics University of Duisburg‐Essen and Center for Nanointegration Duisburg‐Essen (CENIDE) Lotharstr. 1 47057 Duisburg Germany
Thomas Lunkenbein
Fritz-Haber-Institut der Max-Planck-Gesellschaft
Malte Behrens
Faculty of Chemistry University of Duisburg‐Essen Universitätsstr. 7 45141 Essen Germany