Sol-gel derived new high-entropy lanthanide-substituted yttrium iron garnets

In this study, new high-entropy lanthanide-substituted yttrium iron garnet powders Y_2.4Ln_0.6Fe₅O₁₂, where (Ln = Sm, Eu, Gd, Tb), Y_1.8Ln_0.6Ln_0.6Fe₅O₁₂ (with combinations of Sm–Eu, Sm–Gd, Sm–Tb, Eu–Gd, Eu–Tb, Tb–Gd), Y_1.2Eu_0.6Tb_0.6Gd_0.6Fe₅O₁₂, Y_0.6Sm_0.6Eu_0.6Gd_0.6Tb_0·6Fe₅O₁₂, and Y_0.5Sm_0.5Eu_0.5Gd_0.5Tb_0.5Dy_0.5Fe₅O₁₂ were synthesized via an aqueous sol-gel synthesis method and investigated for the first time to the best our knowledge. The phase purity and structure of synthesized mixed-metal garnets were estimated using XRD analysis, FTIR spectroscopy, Raman Spectroscopy and Mössbauer spectroscopy. The sol-gel derived high-entropy garnets exhibited a cubic crystalline structure with space group (Ia-3d) and lattice parameters ranging from 12.355 Å to 12.461 Å depending on substitutional level. The observed Raman spectrum of Y₃Fe₅O₁₂ (YIG) garnet was very similar to previous reported data. More pronounced spectral changes were observed in the Raman spectra after substitution of Y³⁺ ions by higher amount of Ln³⁺ ions. The SEM analysis results revealed that the most particles were formed in the range of 100-300 nm showing rather narrow particle size distribution. SEM-EDX analysis confirmed homogeneous elemental distribution in the high-entropy garnet particles, with an A-site/Fe ratio close to the nominal composition. Magnetic properties of lanthanide-substituted yttrium iron garnets were determined by magnetization measurements. The magnetization dependences of the studied samples had small hysteresis with coercivity H_c of 22-83 Oe and relative remanence M_r/M_s of 0.14-0.47.