Temperature dependent magnetic and structural properties of Al substituted nanostructured hexaferrites with large coercive fields
Abstract
We report a comprehensive study of the temperature-dependent structural, magnetic, vibrational, and dielectric properties of Al-substituted M-type hexaferrites SrFe 12-x Al x O 19 . Neutron powder diffraction and Mössbauer spectrometry show that Al 3+ preferentially replaces Fe 3+ at spin-up octahedral sites (2 a , 12 k ), disrupting the exchange coupling with the spin-down 4 f tetrahedral sites and leading to a progressive reduction of site-specific magnetic moments and a systematic decrease in the Curie temperature, supported by temperature-dependent susceptibility measurements. Raman spectroscopy reveals pronounced phonon anomalies near T C , particularly in modes associated with bipyramidal Fe–O vibrations, reflecting the weakening of both 4 e –12 k and 4 e –4 f exchange pathways. However, the coercive field exhibits a dramatic increase, reaching µ 0 H C ∼ 1.2 T for SrFe 9.6 Al 2.4 O 19, among the largest values reported for this class. Susceptibility measurements suggest that Al substitution, while weakening the superexchange network, contributes to the stabilization of single-domain behavior.
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BibTeX
@article{maltoni2026temperature,
title = {{Temperature dependent magnetic and structural properties of Al substituted nanostructured hexaferrites with large coercive fields}},
author = {Pierfrancesco Maltoni and Ravi Dokala and Prativa Pramanik and Rafael Araujo and Tomas Edvinsson and Sergey Ivanov and Bjarne Almqvist and Gaspare Varvaro and Aldo Capobianchi and Nader Yaacoub and Charles Hervoches and Alberto Martinelli and Robert Pullar and Davide Peddis and Roland Mathieu},
journal = {Acta Materialia},
year = {2026},
month = sep,
doi = {10.1016/j.actamat.2026.122273},
url = {https://hal.science/hal-05747400v1},
note = {CC BY},
}
RIS
TY - JOUR
TI - Temperature dependent magnetic and structural properties of Al substituted nanostructured hexaferrites with large coercive fields
AU - Pierfrancesco Maltoni
AU - Ravi Dokala
AU - Prativa Pramanik
AU - Rafael Araujo
AU - Tomas Edvinsson
AU - Sergey Ivanov
AU - Bjarne Almqvist
AU - Gaspare Varvaro
AU - Aldo Capobianchi
AU - Nader Yaacoub
AU - Charles Hervoches
AU - Alberto Martinelli
AU - Robert Pullar
AU - Davide Peddis
AU - Roland Mathieu
PY - 2026
DA - 2026/09/11
JO - Acta Materialia
DO - 10.1016/j.actamat.2026.122273
UR - https://hal.science/hal-05747400v1
AB - We report a comprehensive study of the temperature-dependent structural, magnetic, vibrational, and dielectric properties of Al-substituted M-type hexaferrites SrFe 12-x Al x O 19 . Neutron powder diffraction and Mössbauer spectrometry show that Al 3+ preferentially replaces Fe 3+ at spin-up octahedral sites (2 a , 12 k ), disrupting the exchange coupling with the spin-down 4 f tetrahedral sites and leading to a progressive reduction of site-specific magnetic moments and a systematic decrease in the Curie temperature, supported by temperature-dependent susceptibility measurements. Raman spectroscopy reveals pronounced phonon anomalies near T C , particularly in modes associated with bipyramidal Fe–O vibrations, reflecting the weakening of both 4 e –12 k and 4 e –4 f exchange pathways. However, the coercive field exhibits a dramatic increase, reaching µ 0 H C ∼ 1.2 T for SrFe 9.6 Al 2.4 O 19, among the largest values reported for this class. Susceptibility measurements suggest that Al substitution, while weakening the superexchange network, contributes to the stabilization of single-domain behavior.
SN - 1359-6454
ER -