Enhancement of maximum energy product in exchange-coupled BaFe12O19/Fe3O4 core-shell-like nanocomposites


Recent economic and environmental concerns have prompted intensive research on the development and optimisation of rare-earth free permanent magnets, in particular of ferrites. M-type barium hexaferrites (BaFe12O19, BaM) are a type of technologically important, low-cost permanent magnet, with high Tc and high resistance to oxidation and corrosion. Their magnetic performance can be improved upon by exploring exchange-coupling mechanisms, to increase their competitiveness with existing rare-earth magnets. The present investigation explores core-shell-like BaM/Fe3O4 nanocomposites, where BaM flake-like particles where prepared via the sol-gel auto-combustion method, and then coated by magnetite spinel nanoparticles via a hydrothermal method, requiring no post-heat treatment. We show how optimised hard to soft magnetic phase ratio and preparation conditions lead to a significant enhancement to the saturation magnetization and remanence, and consequently to an increase of over 75% in the maximum energy product, compared to the parent BaM hexagonal ferrite compound. (C) 2019 Elsevier B.V. All rights reserved.



subject category

Chemistry; Materials Science; Metallurgy & Metallurgical Engineering


Mohseni, F; Pullar, RC; Vieira, JM; Amaral, JS

our authors


This work was developed within the scope of the project CICECO-Aveiro Institute of Materials, POCI-01-0145-FEDER-007679 (FCT Ref. UID/CTM/50011/2013), financed by national funds through the FCT/MEC and when appropriate co-financed by FEDER under the PT2020 Partnership Agreement. R.C. Pullar thanks FCT Grant IF/00681/2015 and J.S. Amaral thanks FCT grant IF/01089/2015 for supporting this work.

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