Abstract <p>This study applies the sol-gel auto combustion approach to achieve the synthesis of iron–nickel–zinc (Fe–Ni–Zn); Fe₂Ni_<i>x</i>Zn₁ _{<i>– x</i>} trimetallic oxide powders using differing amounts of nickel and zinc, whereby <i>x</i> = 0.23, 0.46, and 0.69. DEA (diethanolamine) served as a novel fuel. The resulting calcined samples then underwent analysis via X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM), synchrotron X-ray absorption near edge structure (XANES), and extended X-ray absorption fine structure (EXAFS) analysis to evaluate the phase formation, morphology, particle size, magnetism, local atomic structure, and cation distribution in each case, allowing the systematic characterization of the samples. The XRD analyses clearly revealed that powders that contained differing nickel and zinc components had the major spinel phase along with traces of wurtzite, rock salt, and hematite. The VSM analysis showed that as nickel concentrations increased, trimetallic oxide powders produced a strong rise in saturation magnetization as a result of the increase in net magnetic moment as the cation distribution inside the structure was adjusted. The magneton number variation can be explained by applying the collinear spin ordering model of Néel, while considering how trivalent ions are translocated between sublattices. XANES spectra data indicate that for every sample, the Fe³⁺ ions show synchronicity in their tetrahedral and octahedral coordination with either four or six atoms of oxygen, while in the case of the Ni²⁺ ions the coordination with oxygen is only sixfold, while for Zn²⁺ ions it is fourfold. Finally, the EXAFS spectra confirmed that as the nickel concentration rises, Fe³⁺ ions are translocated from octahedral (<i>B</i>) sites to tetrahedral (<i>A</i>) sites.</p>