Effects of neodymium substitution on the structural, optical, and magnetic properties of yttrium iron garnet nanoparticles

Neodymium (Nd${}^{3+}$)-doped yttrium iron Garnet (YIG) nanoparticles, with compositional variation of Nd${}_x$Y${}_{3-x}$Fe${}_5$O${}_{12}$ (0.0 ≤ x ≤ 3.0), were prepared by co-precipitation method. The prepared nanoparticles were characterized using TGA, XRD, TEM, SEM, EDX, and FTIR. The calcination temperature was chosen according to the maximum decomposition temperature (˃ 810 °C) achieved in TGA. XRD confirmed the successful phase formation, at the chosen sintering temperature (1100 °C), of Garnet for x < 3.0 (cubic Ia3d symmetry), after which the orthoferrite phase NdFeO${}_3$ at x = 3.0 (orthorhombic Pnma symmetry) was formed. The incorporation of Nd${}^{3+}$ increased the lattice parameters (12.3833–12.5020 Å), porosity (34.127–39.549%) and crystallite size (82.66–129.99 nm). Agglomerated, distorted, and irregularly shaped nanoparticles were observed in TEM and SEM with the elemental composition confirmed by EDX, inconsistency with the proposed Nd${}_x$Y${}_{3-x}$Fe${}_5$O${}_{12}$. The FTIR analysis revealed the characteristic bands at 657, 600, and 565 cm${}^{-1}$ with Nd${}^{3+}$ doping concentration between 0.0 and 1.5. These bands disappeared at x = 3.0, where the orthoferrite phase of NdFeO${}_3$ dominated. UV–Vis spectroscopy revealed the semiconducting behavior of the prepared samples with energy gaps ranging between 2.89 and 3.02 eV. A broad emission band was observed, in the range 500–550 nm, in the PL spectra of all the prepared samples in agreement with the calculated band energies. The transport properties were studied by DC conductivity measurements and analyzed by the Arrhenius plots, from which two activation energies were determined for each sample. The magnetic properties, investigated by VSM, showed that isovalent substitution of Y${}^{3+}$ by Nd${}^{3+}$ dramatically influenced room temperature parameters, such as saturation magnetization, coercivity, and remanence magnetization.