Nanocrystalline Dy 3 Fe 5−x Al x O 12 (x = 0.0–1.0) was synthesized by a sol–gel auto-combustion route to investigate the effect of Al 3+ substitution on the structure, local bonding, magnetic behavior, and dielectric response of dysprosium iron garnet nanoparticles. X-ray diffraction confirmed the formation of a single-phase cubic garnet structure for all compositions. Al 3+ substitution led to crystallite refinement, increased microstrain and defect density, and systematic changes in local metal–oxygen bonding, indicating controlled modification of the garnet lattice without loss of phase stability. These structural changes were reflected in the magnetic response, where all samples exhibited soft ferrimagnetic behavior with unsaturated hysteresis loops, low remanence, and low coercivity at room temperature. The observed decrease in magnetization with increasing Al content is attributed to Fe-sublattice dilution and weakened Fe–O–Fe superexchange interactions, while the variation in coercivity is correlated with changes in crystallite size, strain, and microstructural disorder. Dielectric measurements showed strong frequency dispersion consistent with Maxwell–Wagner type polarization, and Al substitution reduced dielectric loss and shifted relaxation features toward higher frequencies, indicating suppressed hopping conduction and improved high-frequency insulating behavior. Overall, this study establishes a clear structure–bonding–property relationship in Al-substituted Dy 3 Fe 5−x Al x O 12 nanogarnets and demonstrates that non-magnetic Al3+ substitution is an effective route for tuning their magnetic and dielectric performance for microwave, magneto-optical, and low-loss dielectric applications. • Al 3+ substitution refines crystallite size and increases lattice microstrain while retaining single-phase garnet. • FTIR analysis shows composition-dependent changes in bond stiffness and elastic constants. • Saturation magnetization decreases due to Fe-sublattice dilution and enhanced spin canting. • Dielectric constant and loss reduce with Al content, with relaxation peaks shifting to higher frequencies. • Al 3+ provides effective tuning of coupled magnetic and dielectric responses in Dy 3 Fe 5-x Al x O 12 nanogarnets.
Bansode et al. (Wed,) studied this question.