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The effects of ‘Sr-doping’ and ‘particle size’ on multiferroic properties of BiFeO 3 nanoparticles were studied. Structural analysis revealed no influence on the rhombohedral structure of BiFeO 3 with Sr-doping in the synthesized nanoparticles. The particle size of Sr-doped BiFeO 3 nanoparticles was tailored by varying calcination temperature. The crystallite size got reduced with Sr-doping and also on decreasing the calcination temperature. Lattice strain was observed to enhance with reducing particle size of Sr-doped BiFeO 3 nanoparticles. Magnetic measurements confirmed enhancement in magnetization via suppression of spin cycloidal structure with Sr-doping owing to creation of oxygen vacancies, enhanced lattice strain and reduction in particle size. Dielectric analysis revealed deterioration of dielectric constant of BiFeO 3 with Sr-doping due to the formation of oxygen vacancies. Further, on reducing particle size of Sr-doped BiFeO 3 nanoparticles, both saturation magnetization and dielectric constant values registered increase. Lowering of the magnetic phase transition temperature with particle size of Sr-doped BiFeO 3 nanoparticles indicated weakening of magnetic exchange interactions. [ABSTRACT FROM AUTHOR]

The undoped and Ca-doped BiFeO3 nanoparticles of different particle size were synthesised using sol-gel. Ca-doping induced structural transformation from rhombohedral to orthorhombic phase along with reduced crystallite size due to its smaller ionic radii. Morphological analysis showed increase in particle size from 11 to 50 nm on increasing calcination temperature from 450 to 650 °C. Magnetic and electrical studies revealed enhancement in magnetism as well as dielectric constant and polarisation values with Ca-doping. When the particle size of Ca-doped BiFeO3 nanoparticles was further reduced, these values registered remarkable enhancement. Thermal analysis revealed charge compensation mechanism to occur via formation of oxygen vacancies on doping of Ca2+ ions in BiFeO3 lattice. The decreasing dielectric constant values indicating increasing oxygen vacancies content with particle size also point towards the similar charge compensation mechanism in the particle size varied Ca-doped BiFeO3 nanoparticles. [ABSTRACT FROM AUTHOR]

The undoped and Ca-doped BiFeO3 nanoparticles of different particle size were synthesised using sol-gel. Ca-doping induced structural transformation from rhombohedral to orthorhombic phase along with reduced crystallite size due to its smaller ionic radii. Morphological analysis showed increase in particle size from 11 to 50 nm on increasing calcination temperature from 450 to 650 °C. Magnetic and electrical studies revealed enhancement in magnetism as well as dielectric constant and polarisation values with Ca-doping. When the particle size of Ca-doped BiFeO3 nanoparticles was further reduced, these values registered remarkable enhancement. Thermal analysis revealed charge compensation mechanism to occur via formation of oxygen vacancies on doping of Ca2+ ions in BiFeO3 lattice. The decreasing dielectric constant values indicating increasing oxygen vacancies content with particle size also point towards the similar charge compensation mechanism in the particle size varied Ca-doped BiFeO3 nanoparticles. [ABSTRACT FROM AUTHOR]

Barium-doped bismuth ferrite (Bi 1− x Ba x FeO 3 ( x =0 and 0.15)) nanoparticles synthesized by a sol–gel method have been found to exhibit strong influence of size on structural, morphological, magnetic and dielectric properties. The size of Ba-doped BiFeO 3 nanoparticle has been tailored via variation of calcination temperature. Structural analysis reveals the stabilization of rhombohedral phase for x =0.15 Ba-substitution in BiFeO 3 lattice. Undoped BiFeO 3 nanoparticles have been found to possess saturation magnetization value of 2.535 emu/g. Ba-substitution, enhancing ferromagnetism by about 1.7 times, is ascribed to suppression of spin cycloidal by oxygen vacancies created due to divalent substitution at trivalent site. Further, this value decreases as the particle size of doped nanoparticles increases owing to the decreasing surface to volume ratio. The magnetic phase transition temperature value registers a decay of 0.86 times with Ba-doping in comparison to undoped BiFeO 3 nanoparticles. Also, the doped nanoparticles exhibit strong particle size dependence. Decreasing magnetic exchange interactions with reducing particle size leads to lowering of Nèel temperature. Ba-substitution has been found to result in decay of dielectric properties by about 0.85 times due to creation of oxygen vacancies. This property further decreases with increasing particle size of doped nanoparticles. These observations reveal strong correlation of size and multiferroism. [ABSTRACT FROM AUTHOR]