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Exchange bias and Verwey transition in Fe5C2/Fe3O4 core/shell nanoparticles
M Xing1, Jeotikanta Mohapatra1, J Elkins1
1Department of Physics, The University of Texas at Arlington, Arlington, Texas 76019, USA. pliu@uta.edu.
Nanoscale
|September 14, 2021
Summary
Exchange bias in iron carbide/magnetite nanoparticles arises from the Verwey transition in the magnetite shell. This phase transition at 125 K induces structural changes, enhancing magnetic coercivity and anisotropy.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Nanotechnology
Background:
- Exchange bias and magnetic properties are crucial for spintronic devices.
- Core/shell nanoparticles offer tunable magnetic characteristics.
- Iron carbide/magnetite (Fe5C2/Fe3O4) composites present unique interfacial phenomena.
Purpose of the Study:
- To investigate exchange bias and magnetic properties in Fe5C2/Fe3O4 core/shell nanoparticles.
- To elucidate the role of the Verwey transition in the observed magnetic phenomena.
- To analyze the correlation between structural and magnetic properties.
Main Methods:
- Synthesis of Fe5C2/Fe3O4 core/shell nanoparticles.
- Temperature-dependent measurements of structural and magnetic properties.
- Analysis of exchange bias field and coercivity.
Main Results:
- Observation of exchange bias linked to the Verwey transition at 125 K.
- Fe3O4 shell transitions from cubic to monoclinic structure during the Verwey transition.
- Enhanced magnetic coercivity due to monoclinic phase's uniaxial anisotropy.
- Abrupt changes in magnetocrystalline anisotropy and exchange coupling at the transition.
Conclusions:
- The Verwey transition in Fe3O4 shells is the origin of exchange bias in Fe5C2/Fe3O4 nanoparticles.
- The monoclinic phase's uniaxial anisotropy significantly enhances magnetic coercivity.
- Understanding these phenomena enables tailored design of magnetic nanomaterials.
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