Formation of Au particles in nonstoichiometric Cu2−x I Cu2 II O3−δ (x ≈ 0.20; δ ≈ 0.10) oxide from aniline + hydrochloric acid mixtures and chloroauric acid in the ratios 30 : 1; 60 : 1; 90 : 1 (S1-S3) by volume and 0.01 mol of copper acetate, Cu(OCOCH3)2.H2O, in each case is performed by sol-gel growth. Powder x-ray diffraction (XRD) results show Au particles are dispersed in tetragonal nonstoichiometric dicopper (I) dicopper (II) oxides, Cu2−x I Cu2 II O3−δ (x ≈ 0.20; δ ≈ 0.10). Average

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... llite sizes of Au particles determined using Scherrer equation are found to be in the approximate ranges ~85−140 Å, ~85−150 Å and ~80−150 Å in S1-S3, respectively which indicate the formation of Au nano-micro size particles in Cu2−x I Cu2 II O3−δ (x ≈ 0.20; δ ≈ 0.10) oxides. Hysteresis behaviour at 300 K having low loop areas and magnetic susceptibility values ~ 5.835×10 −6 −9.889×10 −6 emu/gG in S1-S3 show weakly ferromagnetic nature of the samples. Broad and isotropic electron paramagnetic resonance (EPR) lineshapes of S1-S4 at 300, 77 and 8 K having giso-values ~2.053±0.008−2.304±0.008 show rapid spin-lattice relaxation process in magnetic Cu 2+ (3d 9 ) sites as well as delocalized electrons in Au (6s 1 ) nano-micro size particles in the Cu2−x I Cu2 II O3−δ (x ≈ 0.20; δ ≈ 0.10) oxides. Broad and weak UV-Vis diffuse reflectance optical absorption band ~725 nm is assigned to 2 B1g → 2 A1g transitions, and the weak band ~470 nm is due to 2 B1g → 2 Eg transitions from the ground state 2 B1g (|dx 2 -y 2 >) of Cu 2+ (3d 9 ) ions in octahedral coordination having tetragonal distortion.