We have been synthesized a novel Gd_4-xSr_1+xFe_5-xZn_xO_14+δ [0 ≤ x ≤ 0.45] nanocomposites (NCs) by a facile nitrate-citrate sol–gel process. The microstructural analysis depicted the prepared NCs have a single crystalline phase with an average crystallite size amid 20–35 nm. From FE-SEM and TEM images indicate that the NCs is in hexagonal and spherical like shape. The recorded optical spectra show the intense peak at 583 for Fe²⁺ and Fe³⁺ inter valance charge-transfer. The recorded XPS reveals all possible elements with their favored oxidation state. TGA studies confirmed that the thermal stability of the samples increases with decreasing the Gadolinium oxide content in the sample composition. The VSM analysis confirms the prepared nanocomposites have ferromagnetic nature, which possesses retentivity value at 0.15686 emu/g, 0.18404 emu/g, 0.11337 emu/g, and 0.25010 emu/g. Moreover, the positive control shows the zone of inhibition 27 ± 0.92 mm, 24 ± 1.02 mm, and 20 ± 0.99 mm for E. coli, S. aureus, and B. subtilis. These outcomes indicate that the prepared materials possess fascinating properties for opto-biomedical applications.