CERAMICS INTERNATIONAL Available online at www.sciencedirect.com Ceramics International 39 (2013) 4179–4186 Structural and magnetic properties of the copper ferrite obtained by reactive milling and heat treatment Traian Florin Marinca a,n , Ionel Chicinas- a , Olivier Isnard b a Materials Science and Engineering Department, Technical University of Cluj-Napoca, 103-105 Muncii Avenue, 400641 Cluj-Napoca, Romania b Institut Ne´el, CNRS/Universite´ Joseph Fourier, BP166, 38042 Grenoble, Ce´dex 9, France Received 29 August 2012; received in revised form 30 October 2012; accepted 31 October 2012 Available online 10 November 2012 Abstract Copper ferrite (CuFe 2 O 4 ) was synthesised from an equimolar mixture of copper and iron oxides by mechanosynthesis and subsequent heat treatment. After mechanosynthesis, depending on the milling time, the powder consists in a mixture of phases. The heat treatment at 600 1C did not lead to a complete reaction of the mechano-activated precursors. After the heat treatments at 800 and 1000 1C, the complete formation of copper ferrite for almost all the milling times was noticed. The crystal structure of the copper ferrite was found to be cubic for all the samples heat treated at 1000 1C and a mixture of tetragonal and cubic for the samples heat treated at 800 1C. The amount of copper ferrite with cubic structure predominates in the samples with prolonged milling duration and a decrease of the tetragonal distortion by increasing the milling time occurs. The crystallisation of CuFe 2 O 4 in cubic structure for the samples milled for prolonged time is influenced by the powder contamination with iron. The magnetisations of the samples obtained after heat treatment at 1000 1C were found to be larger compared to the ones of the samples heat treated at 800 1C. The iron contamination, milling duration and heat treatment temperature influence the cations distribution, thus leading to the saturation magnetisation of the copper ferrite samples ranging from 11.9 m B /f.u. to 16.4 m B /f.u. & 2012 Elsevier Ltd and Techna Group S.r.l. All rights reserved. Keywords: A. Milling; B. X-ray methods; C. Magnetic properties; D. Ferrites 1. Introduction Spinel soft ferrites (MeFe 2 O 4 , where Me is metal or a group of metallic elements with 2 þ as total valence) represent one of the most important group of magnetic materials, due to their interesting characteristics. This class of magnetic materials is very important, from both fundamental research and techni- cal applications [1–5]. Their remarkable features are given by their spinel structure. Soft magnetic ferrites are isostructural with the mineral spinel MgAl 2 O 4 . Their complex character- istic crystal structure is a face-centered cubic (space group Fd3m) which has eight formula units in unit cell. For the metallic cations are two crystallographic sites: tetrahedral (A site) and octahedral (B site). The distribution of the metallic cations, Me 2 þ and Fe 3 þ , in tetrahedral and octahe- dral sites (A and B sublattices) has a great importance on the electric and magnetic properties. Typically, there are two types of spinels structures: normal and inverse. In normal spinel, the Me 2 þ cations are positioned in A sites and the Fe 3 þ cations in B sites. In inverse spinel, the Me 2 þ cations are in B sites and the Fe 3 þ cations in both A and B sites. This cations distribution is generally obtained if ferrites are synthesised by classical ceramic route [2,6–9]. Using particular methods such as: sol–gel, mechanosynthesis or co-precipita- tion, various cations distributions are obtained [10–15]. One of the most interesting soft ferrite is copper ferrite, CuFe 2 O 4 . Copper ferrite has inverse spinel structure, with Cu 2 þ cations in octahedral sites if it is classically obtained from oxides by ceramic techniques [2]. A particular feature of CuFe 2 O 4 is the possibility of this compound to crystallise in tetragonal spinel with space group I4 1 /amd. The tetragonal crystal type can be considered as a tetragonally distorted spinel structure with non-standard face-centered space group F4 1 /ddm [16]. The origin of this distortion is a cooperative Jahn–Teller effect which is provoked by the alignment of the Cu 2 þ cations www.elsevier.com/locate/ceramint 0272-8842/$ - see front matter & 2012 Elsevier Ltd and Techna Group S.r.l. All rights reserved. http://dx.doi.org/10.1016/j.ceramint.2012.10.274 n Corresponding author. E-mail address: traian.marinca@stm.utcluj.ro (T.F. Marinca).