Low temperature garnet phase formation in Mn-substituted Y₃Fe_5-xMn_xO₁₂ nanoparticles via citrate combustion synthesis

In this article, we report on the formation of a low-temperature garnet phase in Mn-substituted Y₃Fe_5-xMn_xO₁₂ (x = 0, 0.05, 0.15, and 0.25) nanopowders. We studied the structural, microstructural, static, and dynamic magnetic properties of Mn-substituted Y₃Fe_5-xMn_xO₁₂ (YIG) nanopowders calcined at two different temperatures. The Mn-substituted garnet powders were synthesized using the citrate combustion method followed by calcination at 800 and 1200 °C for 3 h. An increase in Mn substitution (x = 0.15, 0.25) favored the growth of a single garnet phase at low temperatures, even at 800 °C. The lattice constant of these samples ranged from 12.3815 to 12.3679 Å. Microstructural and morphological studies revealed the growth of homogeneous and dense particles, with an average particle size in the range of ∼35–58 nm, close to the single-domain particle size in YIG. Microwave resonance spectra and magnetic hysteresis curves revealed the formation of a ferromagnetic phase in undoped and Mn-doped garnet ferrites at room temperature. The maximum saturation magnetization (26 emu/g) was observed for the sample with Mn content x = 0.05 at 1200 °C, while the largest coercivity (33 Oe) was found for the sample with Mn content x = 0.15 at 1200 °C, among all the samples. The increase in Mn content led to a decrease in peak-to-peak linewidth of FMR spectra from 698.8 to 569.4 G at 800 °C and from 916 to 614.7 G at 1200 °C. This study suggests that Mn substitution in YIG garnet improves structural properties and enhances magnetic anisotropy.