Tuning the multiferroic properties of Pb(Fe1/2Nb1/2)O3 by cationic substitution

A series of substituted lead iron niobate compounds with the general formula Pb((1-x))(2+)A(x)(Z)(Fe{(1-(2-Z)x)/2} Nb{(1+(2-Z)x)/2})O-3 (0<0.6 and A = La3+, K+ or Sr2+) were prepared by a modified solid-state synthesis. The relative concentrations of Fe3+ and Nb5+ were adjusted to compensate the charge imbalance due to the aliovalent substitution. The dielectric constant and magnetic susceptibilities were studied as a function of temperature. The temperature of the dielectric maximum, T-M, of the substituted compounds decreased linearly with increasing concentration of the substituent ions. The magnetic measurements showed an antiferromagnetic transition at temperatures T-N1 due to the superexchange interactions mediated by Fe-O-Fe and an additional anti ferromagnetic-type transition at T-N2. T-N1 linearly increased with the increasing concentration of Fe3+ ion at the B-site of ABO(3)-type substituted compounds. T-M is shown to be directly dependent on the concentration of the ferroactive Nb5+ ions at the B-site and Pb2+ ions at the A-site. (C) 2004 Published by Elsevier B.V.