Cr-substituted Ni–Zn ferrites via oxalate decomposition. Structural, electrical and magnetic properties

•Cr-substituted Ni–Zn ferrites were synthesized through oxalate decomposition route.•Effect of substitution on structural and electromagnetic properties was studied.•Cr-substitution decreases saturation magnetization and increases the coercivity.•Samples showed semiconducting behavior with conductivity decreases by substitution.•An appropriate cation distribution was suggested.

A series of Cr-substituted Ni–Zn ferrites; Ni0.8Zn0.2CrxFe2−xO4 (x=0.0–1.0) were prepared via oxalate decomposition route to characterize the effect of Cr-substitution on structural, magnetic and electrical properties. The prepared powders were characterized using X-ray diffraction (XRD), Fourier transform infrared (FT-IR) and transmission electron microscopy (TEM). XRD indicated single-phase cubic ferrites. The lattice parameters (aExp) exhibited a gradual decrease with increasing chromium, attributed to the smaller ionic radii of Cr3+ substituent. According to the obtained structural data, an appropriate cation distribution was suggested and fortified through FT-IR spectroscopy besides magnetic and electrical measurements. TEM image showed agglomerated cubic crystals with an average size of about 20 nm. Vibrating sample magnetometer (VSM) measurements indicated minimal hysteresis characteristic for soft magnetic material. The decrease in saturation magnetization (Ms) with Cr-substitution was discussed in view of Neel’s two sub-lattice model. The change in the coercivity with Cr-content was discussed in view of estimated cation distribution and magnetization values. The obvious fall in the Curie temperature, estimated from molar susceptibility measurements, with increasing Cr-concentrations was assigned to the gradual replacement of Fe3+ ions on the octahedral sites by paramagnetic Cr3+ ions. ac-conductivity as a function of both frequency and absolute temperature exhibited a semi-conducting behavior. The decrease in conductivity with increasing Cr-content was attributed to the preferential occupation of Cr3+ ions by octahedral sites which replacing Fe3+ ions and limiting Fe2+–Fe3+ conduction.

Graphical abstractThe figure illustrated the variation of the saturation magnetization as well as the coercivity on the amount Cr substitution. From the figure, it is obvious that, the saturation magnetization decreases gradually with increasing Cr-substitution while coercivity increasesFigure optionsDownload full-size imageDownload as PowerPoint slide