Investigation of structual, ferroelectric and magnetic properties of Gd doped BiFeO3 nanoparticles prepared by sol-gel method

Abstract

The nominal compositions of BiFe1-xGdxO3 (x = 0.00, 0.05) nanoparticles were synthesized using sol-gel method to investigate their structural, electrical, magnetic and optical properties. The investigated properties were compared between undoped and Gddoped BiFeO3 nanoparticles. The X-ray diffraction (XRD) patterns revealed that the substitution of Gd in the place of Fe in BiFeO3 induces a tendency of phase transition from rhombohedral to orthorhombic. The field emission scanning electron microscopy images and their respective histograms demonstrated that due to the substitution of Gd, the average particle size was reduced with a narrow size distribution. Particularly, for 5 % Gd doped BiFeO3 annealed at 600 oC the average particle size was reduced up to around ~35 nm which is much smaller than that of undoped BiFeO3. From leakage current density vs. electric field graphs it was observed that the leaky behavior of the synthesized nanoparticles was suppressed due to Gd substitution and increasing annealing temperature. The suppression of leakage current density improved the ferroelectric behavior of the synthesized nanoparticles deduced from polarization vs. electric field hysteresis loops. The dielectric properties of the synthesized nanoparticles follow exactly the same trend of ferroelectric behavior and reduced leakage current density. The magnetization versus magnetic field hysteresis loops were carried out using a Superconducting Quantum Interface Device (SQUID) magnetometer at room temperature. The SQUID analysis demonstrated that, due to the Gd substitution in BiFeO3 nanoparticles the room temperature magnetic parameters such as saturation magnetization (Ms) and remanent magnetization (Mr) decreased gradually with increasing annealing temperature, however, the values of Ms and Mr are many folds higher than their bulk counterparts. The magnetization parameters decreased may be due to the reduction of leakage current and oxygen vacancy related defects and also possibly some structural distortion due to Gd substitution. The band gap energy of the synthesized nanoparticles was determined which indicates that, it is possible to reduce band gap of multiferroic BiFeO3 nanoparticles by doping Gd in the place of Fe.