Abstract
Nanosize spinel ferrite with nominal compositions ZnFe2-xLaxO4, 0.0 <= x <= 0.3, are prepared using stoichiometric amounts of ZnCl2, FeCl3 center dot 6H(2)O, and LaCl3 center dot 7H(2)O by the co-precipitation method. The structures and both the optical and magnetic properties of the prepared samples are investigated. X-ray powder diffraction analysis shows a single-phase cubic spinal structure up to x = 0.2. The lattice parameter a significantly increases with increasing x, which confirms the substitution of La at Fe sites. The crystallite size, estimated by the Scherrer formula, Williamson-Hall method, size-strain plot method, and transmission electron microscope, has been found in the range of 7-14 nm. The Fourier transform infrared (FTIR) spectra indicate the presence of absorption bands in the range of 390-561 cm(-1), which is a common feature of spinel ferrite. The magnetic hysteresis of the investigated samples is studied using the vibrating sample magnetometer (VSM). The saturation magnetization, coercivity, and remanent magnetization have nonsystematic change as the La substitution increases. This is due to the fact that the magnetic properties of nanoferrites are strongly dependent on the cation distribution among tetrahedral and octahedral sites in the cubic spinel structure as well as crystalline size. Electron paramagnetic resonance (EPR) spectra of ZnFe2-xLaxO4 are measured at room temperature in order to study the effect of La substitution on the g value, resonance field (IIr), peak-to-peak line width (Delta IIpp), and spin-spin relaxation time constant (T-2) of the ZnFe2O4 nanoferrite.