Structural and magnetic properties of nanocrystalline Ni 1−xCu xFe 2O 4 prepared through oxalates precursors

Abstract

Spinel ferrites of the composition Ni 1− x Cu x Fe 2O 4 ( x = 0.0–1.0) have been prepared through the thermal decomposition of their respective impregnated oxalates. The oxalate decomposition process was followed using differential thermal analysis–thermogravimetry techniques (DTA–TG). The synthesized nanocrystallites were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FT-IR). The formation of single-phase ferrite is confirmed by XRD. Tetragonal deformation is observed for samples with composition x ⩾ 0.7. The increase in the lattice parameter with increasing Cu content can be explained based on the relative ionic radius. The TEM image shows spherically non-agglomerated particles with an average crystallite size that agrees well with that obtained from XRD. FT-IR studies show two absorption bands ( ν 1 and ν 2) near to 600 and 400 cm −1 for the tetrahedral and octahedral sites, respectively. The hysteresis measurements were done using a vibrating sample magnetometer (VSM). The cation distribution in these compositions is calculated from the magnetization data. With increasing Cu content, the saturation magnetization ( M s) was observed to decrease while the coercivity ( H c) increases. The possible reasons responsible for the composition dependence of the magnetic properties were discussed. The Curie temperature, measured through the temperature dependence of the dc-molar magnetic susceptibility, was found to decrease with increasing Cu content.