The effect of gadolinium substitution in inverse spinel nickel ferrite: Structural, Magnetic, and Mössbauer study


Rare-earth element, Gadolinium, doped NiGdxFe2-xO4 (0 < x < 0.1) materials were synthesized using the sol-gel technique. X-ray diffraction analysis (XRD) showed that the specimens exhibited a single-phase spinel structure up to x = 0.1. The lattice parameter and induced strain increased with an increase in the Gd3+ content. The magnetic parameters derived from hysteresis loops show a decrease in saturation magnetization (Ms) and coercivity (Hc) value with Gd3+ substitution and reaching a value of Ms ∼ 39.13 emu/g and Hc ∼ 110 kOe at x = 0.1. The magnetocrystalline anisotropy, as determined from the Law of Approach to saturation magnetization, is observed to be highest for x = 0.1 at 5K with a large value of K1 ∼ 1.23 × 106 J/m3. The Curie temperature decreased to 898 K at x = 0.1 from 918 for x = 0.0. Hyperfine parameters are derived from fitting room temperature Mössbauer spectra. The Mössbauer spectral analysis indicated that iron was in the Fe3+ state, the magnetic hyperfine field at both the sites tended to decrease, and isomer shift of B site increased while that of A site remained invariant with an increase in the Gd3+ content. Furthermore, migration of Ni2+ from B site to A site was observed with the increase in the Gd3+ occupancy at the B site in the sample. The structural, magnetic, and Mössbauer results are elucidated by the occupancy of Gd3+ at the octahedral (B) site in the inverse spinel NiFe2O4 ferrite.

Publication Title

Journal of Alloys and Compounds