Effect of La3+ ion substitution on the magnetic interaction and grain growth of BaFe2O4 nanoparticles

The pure and La3+ substituted BaFe2O4 with a chemical formula BaLaxFe2-xO4 (x = 0.0, 0.025, 0.050, 0.075, 0.1) were synthesized by sol-gel auto-combustion process: a combustion process involving the reaction of La3+, Fe3+, Ba2+ metal powder. The synthesized samples were annealed at 600 deg C for 4 h. The phase, morphology and particle diameter of the samples were studied by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Observed lower values of porosity and higher values of particle size in La3+ doped samples indicate that La3+ enhance sinterability and thereby promote densification as well as grain growth processes. The crystal lattice constant increases gradually with increasing La substitution. The magnetic properties were measured using a vibrating sample magnetometer (VSM), which indicated that the coercivity of the sample increased and the magnetization decreased with La substitution. The decrease in magnetization values reveals that a partial incorporation of La3+ ions in the spinel matrix can be possible and, thus, a magnetic dilution of octahedral sub-lattice is obtained. Possible explanations for the observed structural and magnetic behavior with various La content are discussed. (author)