Magnetoelastic coupling behaviour of nanocrystalline ε-Fe2O3

Haines, C. R. S. ORCID:, Gich, M., García-Muñoz, J. L., Romaguera, A., Ma, Z., Costa, M. B. and Carpenter, M. A. (2023) Magnetoelastic coupling behaviour of nanocrystalline ε-Fe2O3. Journal of Magnetism and Magnetic Materials, 583. ISSN 0304-8853

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Preparation of a ceramic sample which preserved the nanoscale grain sizes of ∼10–30 nm has allowed elastic and anelastic properties of ε-Fe2O3 to be investigated as functions of temperature and magnetic field strength by Resonant Ultrasound Spectroscopy in the frequency range ∼0.1–1 MHz. Formal analysis of spontaneous strains, e, from previously obtained high resolution lattice parameter data confirmed that magnetic ordering below ∼500 K is accompanied by strains of up to ∼±0.002 due to coupling with the order parameter, m, according to λem2. However, this coupling does not result in elastic softening that would be expected if the order parameter relaxed in response to an induced strain on the timescale of the acoustic resonances. Stiffening or softening during heating through ∼450–480 K of the initial as prepared material, which acquired a distinct magnetisation parallel to the stress applied during Spark Plasma Sintering, is attributed to changes in magnetic domain configurations involving preferred local alignments of individual moments of monodomain crystals. The crystallographic space group, Pna21, and magnetic space group at room temperature, Pna'21', allow ε-Fe2O3 to be both piezoelectric and piezomagnetic. It is postulated that changes in the effective coefficients of these properties for bulk samples are responsible for the observed variations in acoustic resonance frequencies according to the magnetic domain structure present. No elastic or anelastic anomalies were observed at the commensurate-incommensurate transition near 110 K. Instead, acoustic resonance frequencies changed in response to an applied magnetic field, consistent with viscous motion of magnetic domain walls and the effect of poling on piezo coefficients. Ceramic samples of ε-Fe2O3 could have potentially functional piezoelectric and/or piezomagnetic properties that are tunable by choice of magnetic and thermal history.

Item Type: Article
Additional Information: Funding Information: This work was funded by grant no. RPG-2016-298 from the Leverhulme Trust. RUS facilities in Cambridge were established through grants from the Natural Environment Research Council (Grants No. NE/B505738/1 and No. NE/F017081/1) and the Engineering and Physical Sciences Research Council (Grant No. EP/I036079/1) to MAC. We also acknowledge financial support from the Spanish Ministry of Science, Innovation, and Universities (Grants No. RTI2018-098537-B-C21, cofunded by ERDF from EU, and FUNFUTURE (CEX2019-000917-S)) and funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No. 819623). ALBA synchrotron is also acknowledged. Support is acknowledged from the European Union Horizon 2020 Research and Innovation Programme under Marie Skłodowska-Curie grant 861046 (BIOREMIA) for MBC.
Uncontrolled Keywords: magnetic phase transition,magnetoelastic coupling,nanocrystalline,strain relaxation,ε-fe o,electronic, optical and magnetic materials,condensed matter physics ,/dk/atira/pure/subjectarea/asjc/2500/2504
Faculty \ School: Faculty of Science > School of Physics
UEA Research Groups: Faculty of Science > Research Groups > Centre for Photonics and Quantum Science
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Depositing User: LivePure Connector
Date Deposited: 23 Jun 2023 08:31
Last Modified: 01 Aug 2023 13:31
DOI: 10.1016/j.jmmm.2022.170240


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