Verma, Kuldeep Chand and Kotnala, R. K.
(2016)
Tailoring the multiferroic behavior in BiFeO3 nanostructures by Pb doping.
RSC Advances , 6 (62).
S7727-S7738.
ISSN 2046-2069
Abstract
The weak and deficient manipulation of charge-spin coupling in multiferroic BiFeO3 (BFO) notoriously limits device applications. To mould the spontaneous charge and the spin orientation synergistically in BFO, in this paper Pb2+ substitution for Bi3+ could induce lattice distortions and structural phase transitions to tune the lone-pair activity (6s(2)) for ferroelectricity and neutralized oxygen vacancies to valence Fe2+/Fe3+ superexchange for ferromagnetism. Multiferroic Bi1-xPbxFeO3 [x = 0, 0.05, 0.075 and 0.1] nanostructures were synthesized by a chemical combustion process. X-Ray diffraction confirms the distorted rhombohedral BFO structure and the lattice expansion with Pb doping. The Pb ions also modified the shape of the BFO nanostructures. The observed ferroelectric behavior depends upon lattice distortion, reduction in oxygen vacancies to induce low leakage current and the shape/size effect in BFO nanostructures. The zero field (ZFC) and field cooling (FC) SQUID measurement confirm the strength of antiferromagnetism in BFO with Pb2+ ions. The cusp in ZFC magnetization is studied by ac magnetic susceptibility measurements that include spin-glass and superparamagnetic interactions in antiferromagnetism at low temperature. The oxidation states in BFO suggest oxygen vacancies that are reduced with Pb doping and maintain Fe2+/Fe3+ valences. The dielectric permittivity changes with applied dc magnetic field, which could induce a magnetodielectric effect due to spin pair correlation of neighboring spins and the coupling constant. Furthermore, significant dielectric anomalies appear near both the ferroelectric phase transition, and the Neel temperature of BFO implies the magnetoelectric coupling.
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