Metastable Crystalline Cobalt Iron Oxide Nano‐Flakes with Antiferromagnetic/Ferrimagnetic Composition Mosaicity
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<sub>2</sub>O<sub>4</sub>-like and Co<sub>3</sub>O<sub>4</sub>-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.
Authors
- Malte Behrens (ORCID: https://orcid.org/0000-0003-3407-5011)
- Oliver Gutfleisch (ORCID: https://orcid.org/0000-0001-8021-3839)
- Arno Bergmann (ORCID: https://orcid.org/0000-0001-5071-6806)
- Anna Rabe (ORCID: https://orcid.org/0000-0002-9049-4002)
- David Kordus (ORCID: https://orcid.org/0000-0002-9481-2194)
- Thomas Lunkenbein (ORCID: https://orcid.org/0000-0002-8957-4216)
- Janis Timoshenko (ORCID: https://orcid.org/0000-0003-2963-3912)
- Heiko Wende (ORCID: https://orcid.org/0000-0001-8395-3541)
- Thomas Götsch (ORCID: https://orcid.org/0000-0003-3673-317X)
- Shohreh Rafiezadeh (ORCID: https://orcid.org/0009-0005-8960-578X)
- Soma Salamon (ORCID: https://orcid.org/0000-0002-8661-6038)
- Joachim Landers (ORCID: https://orcid.org/0000-0002-4506-6383)
- Rossitza Pentcheva (ORCID: https://orcid.org/0000-0002-4423-8980)
- Franz Schmidt (ORCID: https://orcid.org/0000-0003-0125-2704)
- Benedikt M. Beckmann (ORCID: https://orcid.org/0000-0001-7566-4408)
- Clara Rettenmaier (ORCID: https://orcid.org/0000-0001-5654-4478)
- Beatriz Roldán Cuenya (ORCID: https://orcid.org/0000-0002-8025-307X)
- Mauricio López Luna (ORCID: https://orcid.org/0000-0003-0285-7860)
- Matthias Eckhardt (ORCID: https://orcid.org/0000-0003-1964-9064)
- Christoph Pratsch (ORCID: https://orcid.org/0000-0003-4315-4854)
- Felix T. Haase (ORCID: https://orcid.org/0000-0003-1646-4312)
- Mirijam Zobel (ORCID: https://orcid.org/0000-0002-8207-8316)
- Axel Knop‐Gericke (ORCID: https://orcid.org/0009-0008-1149-4102)
Institutions
- Helmholtz-Zentrum Berlin für Materialien und Energie (DE)
- Fritz Haber Institute of the Max Planck Society (DE)
- Hochschule für Angewandte Wissenschaften Kiel (DE)
- Technische Universität Darmstadt (DE)
- Max Planck Institute for Chemical Energy Conversion (DE)
- University of Bayreuth (DE)
- University of Duisburg-Essen (DE)
- RWTH Aachen University (DE)
Publication Details
- Journal
- Angewandte Chemie International Edition
- Published
- 2025-10-21
- DOI
- https://doi.org/10.1002/anie.202504171
- Primary Topic
- Magnetic Properties and Synthesis of Ferrites
- Type
- article
- Field-Weighted Citation Impact
- 0.00
Funders
- U.S. Department of Energy
- Deutsche Forschungsgemeinschaft
- Bundesministerium für Bildung und Forschung
- Office of Science
- Basic Energy Sciences
- SLAC National Accelerator Laboratory