Field-induced spin cycloidal modulation to antiferromagnetic transition and possible flexomagnetic effect in BiFeO3 nanoparticles

Beyond its various properties, the model multiferroic BiFeO3 (BFO) displays a rich magnetic structure illustrated in the bulk by its long period (∼62 nm) spin cycloidal modulation. Here, BFO nanoparticles are produced by a facile hydrothermal method and show average size of 8 nm and a narrow size di...

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Bibliographic Details
Published in:Journal of alloys and compounds 2023-02, Vol.934, p.167944, Article 167944
Main Authors: Mallek-Zouari, I., Ben Taazayet, W., Grenèche, J.-M., Bessais, L., Dkhil, B., Thabet Mliki, N.
Format: Article
Language:English
Subjects:
Multiferroic hydrothermal method DRX Transmission Electron microscopy Mössbauer spectroscopy magnetic characterization
Physics
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Summary:Beyond its various properties, the model multiferroic BiFeO3 (BFO) displays a rich magnetic structure illustrated in the bulk by its long period (∼62 nm) spin cycloidal modulation. Here, BFO nanoparticles are produced by a facile hydrothermal method and show average size of 8 nm and a narrow size distribution, as determined using x-ray diffraction analysis and transmission electron microscopy images. Mössbauer spectrometry (MS) unambiguously reveals that a cycloidal modulation does still exists with particles about 5 times smaller than the bulk cycloid. Combining macroscopic magnetic measurements and in situ Mössbauer spectrometry, we demonstrate that a critical magnetic field of ∼0.2 T destabilizes the cycloidal modulation to lead to a homogenous antiferromagnetic state, as the result of magnetic anisotropy due to magnetoelastic and surface-confinement effects. More interestingly, further increasing of the external magnetic field up to 8 T does not change the average magnetic hyperfine field and results into multiple Mössbauer sextets we propose to explain by a flexomagnetic effect i.e. magnetic anisotropies resulting from strain gradients due to a continuous variation of the coupling between magnetization and the structural distortion from the surface to the particle core. •Successful synthesis of 8 nm BFO nanoparticles by a facile hydrothermal process.•XRD analysis and TEM characterization.•Demonstration of the destabilization of cycloidal modulation by combining macroscopic magnetic measurements and in situ Mössbauer spectroscopy.
ISSN:0925-8388
1873-4669
DOI:10.1016/j.jallcom.2022.167944