Magneto-dielectric and thermal study of Gd-doped nano nickelates

The Ni1-xGdxFe2O4 (x = 0.02-0.08) (NGF) nanoparticles were synthesized via hydrothermal method. The X-ray diffraction study confirmed the single-phase cubic spinel structure. The Da value decreases from 25 to 19 nm (strain increases from 0.0438 to 0.0613) (for x = 0.2-0.4). Further, it is increased to 43 nm (strain decreases from 0.0283 to 0.0138) from x = 0.4-0.8. The morphology indicated the stones (approximately nanocubes) like structures in the FESEM images. The mass loss and thermal transition temperatures were evaluated as a function of Gd-content using TG-DTG and TG-DSC measurements. The high mass reduction was observed for x = 0.02 (7.81%) and 0.04 (8.45%). The M-H loops evidenced the high magnetization values ranging between 49.1 and 62.1 emu/g for NGF as compared to pure nickel ferrite. Cation distribution evidenced the concentration of each cation at A- and B-site. The dielectric, conductivity, and impedance parameters were elucidated with frequency and 'x'. The Maxwell-Wagner polarization is noticed at low frequency. The short- and long-range polarization mechanisms were found in the dielectric modulus plots. The impedance analysis shows the partial relaxation behavior of samples.