Formation of the hard-magnetic epsilon iron oxide phase from akaganéite nanoparticles

Navya Joseph; Surya Gopi; Aladin Ullrich; Manfred Albrecht; Senoy Thomas

doi:10.1088/1361-6528/ad844f

Formation of the hard-magnetic epsilon iron oxide phase from akaganéite nanoparticles

Nanotechnology. 2024 Oct 17;36(2). doi: 10.1088/1361-6528/ad844f.

Authors

Navya Joseph¹, Surya Gopi¹, Aladin Ullrich², Manfred Albrecht², Senoy Thomas¹

Affiliations

¹ Department of Physics, Cochin University of Science and Technology, Cochin 682022 Kerala, India.
² Institute of Physics, University of Augsburg, Universitätsstraße 1 Nord, D-86159 Augsburg, Germany.

PMID: 39417687
DOI: 10.1088/1361-6528/ad844f

Abstract

Elongated akaganéite (β-FeOOH) nanoparticles were prepared by a forced hydrolysis route using FeCl₃·6H₂O employing various urea concentrations.β-FeOOH nanoparticles stabilized within the SiO₂matrix were annealed at different temperatures, ranging from 500 °C to 1300 °C. It was observed thatβ-FeOOH underwent a temperature-induced conversion toγ-Fe₂O₃and subsequently toϵ-Fe₂O₃. Due to theϵ-Fe₂O₃phase formation, the coercivity rapidly increased to 16 kOe for samples annealed at 900 °C and reached values up to 21.5 kOe when annealed at 1200 °C. At a higher temperature of 1300 °C, theϵ-Fe₂O₃phase transforms mainly into theα-Fe₂O₃phase, which causes the coercivity to rapidly drop to negligible values.

Keywords: epsilon-iron oxide; hard magnetic materials; magnetic nanoparticles.