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Suppression of the Verwey Transition by Charge Trapping |
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| Authors: | Carolin Schmitz‐Antoniak Detlef Schmitz Anne Warland Masih Darbandi Soumyajyoti Haldar Sumanta Bhandary Biplab Sanyal Olle Eriksson Heiko Wende |
| Institution: | 1. Peter‐Grünberg‐Institut (PGI‐6), Forschungszentrum Jülich, Jülich, Germany;2. Helmholtz‐Zentrum Berlin für Materialien und Energie, Berlin, Germany;3. Fakult?t für Physik and Center for Nanointegration Duisburg‐Essen (CENIDE), Universit?t Duisburg‐Essen, Duisburg, Germany;4. Chemistry faculty, University of Tabriz, Tabriz, Iran;5. Institute of Theoretical Physics & Astrophysics, University of Kiel, Kiel, Germany;6. Centre de Physique Théorique (CPHT), Ecole Polytechnique, Palaiseau cedex, France;7. Division of Materials Theory, Department of Physics and Astronomy, Uppsala University, SE, Uppsala, Sweden;8. School of Science and Technology, ?rebro University, ?rebro, Sweden |
| Abstract: | The Verwey transition in Fe3O4 nanoparticles with a mean diameter of 6.3 nm is suppressed after capping the particles with a 3.5 nm thick shell of SiO2. By X‐ray absorption spectroscopy and its associated X‐ray magnetic circular dichroism this suppression can be correlated to localized Fe2+ states and a reduced double exchange visible in different site‐specific magnetization behavior in high magnetic fields. The results are discussed in terms of charge trapping at defects in the Fe3O4/ SiO2 interface and the consequent difficulties in the formation of the common phases of Fe3O4. By comparison to X‐ray absorption spectra of bare Fe3O4 nanoparticles in course of the Verwey transition, particular changes in the spectral shape could be correlated to changes in the number of unoccupied d states for Fe ions at different lattice sites. These findings are supported by density functional theory calculations. |
| Keywords: | magnetite nanoparticles Verwey transition X‐ray absorption spectroscopy |