Mössbauer, Infrared and X-ray Studies for Ni_{0.5}Zn_{0.5}Cr_xFe_{2-x}O_4 Ferrites


Abstract: Spinel ferrites of the system Ni_{0.5}Zn_{0.5}Cr_xFe_{2-x}O_4, 0 \le x \le 1, have been studied via Mössbauer, IR and X-ray spectra. Mössbauer spectra of the samples showed broad six-line patterns and a central paramagnetic phase. The spectra have been analyzed to two magnetic patterns, A and B, and two quadrupole doublets, C_A and C_B. The patterns A and C_A are assigned to Fe^{3+} ions at the tetrahedral A-sites and the patterns B and C_B to Fe^{3+} and Fe^{2+} ions at the octahedral B-sites. The deduced hyperfine interaction parameters; the isomer shifts, quadrupole splitting, outermost line widths, hyperfine magnetic fields and bulk magnetization were studied and discussed as functions of the Cr^{3+} additions x. The cation distribution of the compounds was estimated using the site preference of elements and the area ratio of B- to A-sites. The broad magnetic pattern B has been fitted to several subpatterns. Using the obtained hyperfine parameters one could assign each of the B-subpatterns to a component depends on the number of nonmagnetic Zn^{2+} ions as A-site nearest neighbours of the Fe ions at the B-sites. Five absorption bands were observed in the infrared spectra in the range between 1100 and 200 cm^{-1}. These bands are assigned to the Fe^{3+} ions on A-sites; to Fe^{3+} and Cr^{3+} ions on B-sites; to divalent ions Fe^{2+} and Ni^{2+} and to the energy of the lattices. The existence of Fe^{2} ions on the A- and B-sites has been confirmed. From X-ray analysis, the average, true, and theoretical lattice parameters, the theoretical and bulk densities, the porosity, the oxygen parameter and the ionic radii, bonds, edges and hopping lengths of the A- and B-sites have been calculated and discussed depending on the Cr^{3+} ion content x. The dependency of the hyperfine field on the hopping length at the A- and B-sites has been studied and discussed.

Keywords: Mössbauer, Infrared, X-ray and ferrites.

Full Text: PDF