Mossbauer and Structural Properties of La-Substituted Ni0.4Cu0.2Zn0.4Fe2O4 Nanocrystalline Ferrite

In this paper, La3+ substituted Ni0.4Cu0.2Zn0.4Fe2-xLaxO4(0 <= x <= 0.15) ferrite was prepared by using a sol gel auto-combustion route. X-ray diffraction (XRD) analysis of the compound calcined at 800 degrees C for 3 h showed cubic spinet ferrites and crystalline size decreases sharply. Extra phase of LaFe03 emerges when X?: 0.05 and the crystalline sizes increase linearly at high temperature 950 degrees C for 3 h. The Mossbauer spectra at room temperature of samples calcined at 800 degrees C for 3 h vary from magnetic sextets to shrink magnetic sextet and collapse to relaxation doublet (x = 0.1). This variation of magnetic order state confirmed the Fe3+-O-2-Fe3+ super exchange interaction decrease due to La3+ substitutions. When calcined at 950 degrees C for 3 h, the hyperfine magnetic field distribution probability moves to high magnetic field region. The magnetic order for all samples exhibits relaxation sextet magnetic spectra and does not change obviously up to substitution x = 0.15. The super exchange interactions have been enhanced and the Curie temperature increases. Scanning electron microscopy (SEM) images showed that the specimens doped with rare earth (RE) ions have small particle size and large compactness which can be attributed to the inductive effect of LaFeO3 phase at x = 0.05.