International Journal of Technology and Applied Science

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Volume 17 Issue 11
November 2026

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Impact of Cerium and Gadolinium Doping on the Optical and Magnetic Behaviour of Nickel Ferrites

Author(s) Dr. B. Sreematha
Country India
Abstract The rare-earth substitution is a useful means for controlling the electronic and magnetic properties of spinel ferrites. The nickel ferrite nanoparticles, NiFe2−xRxO4 (R = Ce, Gd; x = 0.000–0.100), were synthesized using citrate sol–gel auto-combustion and calcined at 700 °C. The X-ray powder diffraction showed the cubic inverse-spinel lattice structure of NiFe2O4 with minor secondary phases such as CeO2 and GdFeO3 appearing above x = 0.025. The lattice parameter increased from 8.338 Å to 8.360 Å (Ce) and 8.353 Å (Gd), and the crystallite size decreased from 28.4 nm to 21.5 nm and 22.7 nm, respectively. An increase in Urbach energy, indicating increased structural disorder, and a direct band-gap widening from 2.12 eV to 2.31 eV (Ce) and 2.38 eV (Gd) were found by Tauc analysis of the diffuse-reflectance spectra. From the room-temperature hysteresis loops, it is seen that substitution of Ce3+ ions continuously decreased the saturation magnetization from 48.2 to 38.0 emu/g, whereas substitution of Gd3+ ions gave a maximum value of 52.4 emu/g at x = 0.050 and then gradually decreased. Both dopants caused a decrease in coercivity, which is considered a magnetic softening. Contrasting behaviour is explained in terms of differences in ionic radius, site preference, 4f – 3d exchange, and secondary-phase formation. The compositions around x = 0.05 have the best combination of tunable band gap and increased magnetization.
Keywords Nickel ferrite; cerium; gadolinium; optical band gap; saturation magnetization; sol–gel auto-combustion; rare-earth doping
Published In Volume 17, Issue 11, November 2026
Published On 2026-11-07
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