Epsilon iron oxide: origin of the high coercivity stable low Curie temperature magnetic phase found in heated archeological materials

Lopez-Sanchez, J., McIntosh, G., Osete, M., del Campo, A., Villalain, J., Perez, L., Kovacheva, M. and Rodriguez de la Fuente, O. (2017) Epsilon iron oxide: origin of the high coercivity stable low Curie temperature magnetic phase found in heated archeological materials. Geochemistry, Geophysics, Geosystems, 18. pp. 2646-2656. ISSN 1525-2027.

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Abstract

The identification of epsilon iron oxide (ɛ-Fe2O3) as the low Curie temperature high coercivity stable phase (HCSLT) carrying the remanence in heated archeological samples has been achieved in samples from two archeological sites that exhibited the clearest evidence of the presence of the HCSLT. This uncommon iron oxide has been detected by Confocal Raman Spectroscopy (CRS) and characterized by rock magnetic measurements. Large numbers of ɛ-Fe2O3 microaggregates (in CO) or isolated clusters (in HEL) could be recognized, distributed over the whole sample, and embedded within the ceramic matrix, along with hematite and pseudobrookite and with minor amounts of anatase, rutile, and maghemite. Curie temperature estimates of around 170°C for CO and 190°C for HEL are lower than for pure, synthetic ɛ-Fe2O3 (227°C). This, together with structural differences between the Raman spectra of the archeologically derived and synthetic samples, is likely due to Ti substitution in the ɛ-Fe2O3 crystal lattice. The γ-Fe2O3-ɛ-Fe2O3-α-Fe2O3 transformation series has been recognized in heated archeological samples, which may have implications in terms of their thermal history and in the factors that govern the formation of ɛ-Fe2O3.

Item Type: Article
Subjects: B Philosophy. Psychology. Religion > BL Religion > BL0660 History and principles of religions > BL1000 Asian. Oriental > BL1100 Hinduism > BL1109.2 Antiquities. Archaeology. Inscriptions
Q Science > QC Physics > QC0801 Geophysics. Cosmic physics
Divisions: Faculty of Social and Applied Sciences > School of Human and Life Sciences
Depositing User: Gregg McIntosh
Date Deposited: 28 Nov 2017 17:16
Last Modified: 12 Dec 2017 14:49
URI: https://create.canterbury.ac.uk/id/eprint/16251

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Last edited: 29/06/2016 12:23:00