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Tuning Exchange Coupling in NiO-Based Bimagnetic Heterostructured Nanocrystals
Abdullah Al Shafe1, Mohammad Delower Hossain2, Robert A Mayanovic1
1Department of Physics, Astronomy and Materials Science, Missouri State University, Springfield, Missouri 65897, United States.
ACS Applied Materials & Interfaces
|May 17, 2021
Summary
Researchers synthesized bimagnetic heterostructured nanocrystals with tunable magnetic properties by controlling pH during hydrothermal synthesis. These NiO/Mn-Ni-O and NiO/Mn3O4 nanocrystals show potential for magnetic devices and biomedical applications.
Area of Science:
- Materials Science
- Nanotechnology
- Magnetism
Background:
- Bimagnetic heterostructured nanocrystals combine properties of different magnetic materials.
- Controlling nanoscale structure is crucial for tuning magnetic properties like coercivity and exchange bias.
- Antiferromagnetic NiO and ferrimagnetic Mn-Ni-O/Mn3O4 offer potential for advanced magnetic applications.
Purpose of the Study:
- To synthesize bimagnetic heterostructured nanocrystals with varying NiO core overgrowths.
- To investigate the influence of aqueous solution pH on nanocrystal structure and magnetic properties.
- To explore the potential of these materials for magnetic devices and biomedical applications.
Main Methods:
- Two-step synthesis: thermal decomposition for NiO core, followed by hydrothermal growth of Mn-Ni-O and/or Mn3O4 overgrowth.
- Controlled hydrothermal synthesis at pH values ranging from 2.4 to 7.0.
- Characterization using Transmission Electron Microscopy (TEM), X-ray Diffraction (XRD) with Rietveld refinement, and magnetic property measurements (temperature-dependent magnetization, hysteresis loops).
Main Results:
- Three types of heterostructures were identified based on pH: NiO/Mn-Ni-O core-shell, mixed NiO/Mn-Ni-O/Mn3O4 core-overgrowth, and NiO/Mn3O4 core-island.
- Magnetic coercivity and exchange bias varied systematically with pH, with NiO/Mn3O4 core-island structures (pH 5.0) exhibiting the largest values (nearly 6 kOe and 3 kOe, respectively).
- Density Functional Theory (DFT) calculations confirmed ferrimagnetic properties of Mn-Ni-O and a larger magnetic anisotropy constant for Mn3O4 compared to Mn-Ni-O.
Conclusions:
- Hydrothermal deposition offers tunable control over the structure and magnetic properties of NiO-based bimagnetic heterostructures.
- The pH-dependent synthesis allows for optimization of coercivity and exchange bias, achieving significant values in NiO/Mn3O4 core-island nanocrystals.
- These tunable heterostructured nanocrystals are promising candidates for magnetic device and biomedical applications.
Keywords:
coercivitydensity functional theoryexchange biashydrothermal synthesismagnetic propertiesmagnetocrystalline anisotropynanocrystalstransmission electron microscopyMore Related Videos
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