Origin of enhanced multiferroic properties in Dy and Co co-doped BiFeO3 ceramics

Abstract

Structural, magnetic and ferroelectric properties of polycrystalline BiFeO3, Bi0.9Dy0.1FeO3, BiFe0.97Co0.03O3 and Bi0.9Dy0.1Fe0.97Co0.03O3, which were prepared by solid-state method, have been investigated. The X-ray diffraction (XRD) patterns reveal that all the samples are in single phase and show rhombohedrally distorted perovskite structure with R3c space group. Both XRD and Raman-scattering studies show that Dy and Co co-doped sample has a compressive lattice distortion induced by co-substitution of Dy and Co ions at the A and the B sites, respectively. Dy and Co co-doping favors weak ferromagnetism ordering with evident magnetic hysteresis loop and enhances magnetization values at room temperature. Ferroelectric hysteresis loop for Dy and Co co-doped sample shows the nearly saturated polarization at 40 kV/cm and large remnant polarization. Dy dopant is prominent in the reduced leakage current density, while Co dopant is remarkable in the improved remnant magnetization in Bi0.9Dy0.1Fe0.97Co0.03O3 ceramic. By using a simple model, it was found that the anharmonicity of canted spiral cycloidal spin structure was responsible for the weak ferromagnetism of pure BiFeO3, and the enhanced magnetization in Co-doped sample was attributed to the transition from the incommensurate cycloidal spiral spin structure towards the G-type canted collinear antiferromagnetic structure.