abstract
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.
keywords
BARIUM HEXAFERRITE; MAGNETIC-PROPERTIES; REMANENCE; ALLOYS; SOFT
subject category
Chemistry; Materials Science; Metallurgy & Metallurgical Engineering
authors
Mohseni, F; Pullar, RC; Vieira, JM; Amaral, JS
our authors
Farzin Mohseni
PhD Student
João Cunha de Sequeira Amaral
Assistant Researcher
Joaquim Manuel Vieira
Retired Professor
Rob Pullar
CollaboratorGroups
G2 - Photonic, Electronic and Magnetic Materials
G4 - Renewable Materials and Circular Economy
Projects
CICECO - Aveiro Institute of Materials (UID/CTM/50011/2013)
Projeto de Investigação Exploratória: João Amaral (IF/01089/2015)
acknowledgements
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.