Local structure and magnetism of Fe2O3 maghemite nanocrystals : The role of crystal dimension
(2020) In Nanomaterials 10(5).- Abstract
Here we report on the impact of reducing the crystalline size on the structural and magnetic properties of γ-Fe2O3 maghemite nanoparticles. A set of polycrystalline specimens with crystallite size ranging from ~2 to ~50 nm was obtained combining microwave plasma synthesis and commercial samples. Crystallite size was derived by electron microscopy and synchrotron powder diffraction, which was used also to investigate the crystallographic structure. The local atomic structure was inquired combining pair distribution function (PDF) and X-ray absorption spectroscopy (XAS). PDF revealed that reducing the crystal dimension induces the depletion of the amount of Fe tetrahedral sites. XAS confirmed significant bond... (More)
Here we report on the impact of reducing the crystalline size on the structural and magnetic properties of γ-Fe2O3 maghemite nanoparticles. A set of polycrystalline specimens with crystallite size ranging from ~2 to ~50 nm was obtained combining microwave plasma synthesis and commercial samples. Crystallite size was derived by electron microscopy and synchrotron powder diffraction, which was used also to investigate the crystallographic structure. The local atomic structure was inquired combining pair distribution function (PDF) and X-ray absorption spectroscopy (XAS). PDF revealed that reducing the crystal dimension induces the depletion of the amount of Fe tetrahedral sites. XAS confirmed significant bond distance expansion and a loose Fe-Fe connectivity between octahedral and tetrahedral sites. Molecular dynamics revealed important surface effects, whose implementation in PDF reproduces the first shells of experimental curves. The structural disorder affects the magnetic properties more and more with decreasing the nanoparticle size. In particular, the saturation magnetization reduces, revealing a spin canting effect. Moreover, a large effective magnetic anisotropy is measured at low temperature together with an exchange bias effect, a behavior that we related to the existence of a highly disordered glassy magnetic phase.
(Less)
- author
- organization
- publishing date
- 2020-04-30
- type
- Contribution to journal
- publication status
- published
- subject
- keywords
- Disordered magnetism, Finite size effects, Maghemite, Molecular dynamics, Pair distribution function, X-ray absorption spectroscopy
- in
- Nanomaterials
- volume
- 10
- issue
- 5
- article number
- 867
- publisher
- MDPI AG
- external identifiers
-
- pmid:32365930
- scopus:85085044880
- ISSN
- 2079-4991
- DOI
- 10.3390/nano10050867
- language
- English
- LU publication?
- yes
- id
- 2ddce65d-185c-4320-b169-0d67ae20a7db
- date added to LUP
- 2020-06-17 16:16:53
- date last changed
- 2024-05-30 17:31:44
@article{2ddce65d-185c-4320-b169-0d67ae20a7db, abstract = {{<p>Here we report on the impact of reducing the crystalline size on the structural and magnetic properties of γ-Fe<sub>2</sub>O<sub>3</sub> maghemite nanoparticles. A set of polycrystalline specimens with crystallite size ranging from ~2 to ~50 nm was obtained combining microwave plasma synthesis and commercial samples. Crystallite size was derived by electron microscopy and synchrotron powder diffraction, which was used also to investigate the crystallographic structure. The local atomic structure was inquired combining pair distribution function (PDF) and X-ray absorption spectroscopy (XAS). PDF revealed that reducing the crystal dimension induces the depletion of the amount of Fe tetrahedral sites. XAS confirmed significant bond distance expansion and a loose Fe-Fe connectivity between octahedral and tetrahedral sites. Molecular dynamics revealed important surface effects, whose implementation in PDF reproduces the first shells of experimental curves. The structural disorder affects the magnetic properties more and more with decreasing the nanoparticle size. In particular, the saturation magnetization reduces, revealing a spin canting effect. Moreover, a large effective magnetic anisotropy is measured at low temperature together with an exchange bias effect, a behavior that we related to the existence of a highly disordered glassy magnetic phase.</p>}}, author = {{Coduri, Mauro and Masala, Paolo and Bianco, Lucia Del and Spizzo, Federico and Ceresoli, Davide and Castellano, Carlo and Cappelli, Serena and Oliva, Cesare and Checchia, Stefano and Allieta, Mattia and Szabo, Dorothee Vinga and Schlabach, Sabine and Hagelstein, Michael and Ferrero, Claudio and Scavini, Marco}}, issn = {{2079-4991}}, keywords = {{Disordered magnetism; Finite size effects; Maghemite; Molecular dynamics; Pair distribution function; X-ray absorption spectroscopy}}, language = {{eng}}, month = {{04}}, number = {{5}}, publisher = {{MDPI AG}}, series = {{Nanomaterials}}, title = {{Local structure and magnetism of Fe<sub>2</sub>O<sub>3</sub> maghemite nanocrystals : The role of crystal dimension}}, url = {{http://dx.doi.org/10.3390/nano10050867}}, doi = {{10.3390/nano10050867}}, volume = {{10}}, year = {{2020}}, }