In the present work, 5 MeV Si++ ions for the ion fluence of 1 x 1016 cm-2 and 325 keV Mn+2 ions for the fluence of 2 x 1016 cm-2 co-implanted into un-doped GaN film of thickness 1.90 μm, grown on sapphire substrate. Structural, optical and magnetic properties of non-implanted , Mn-implanted and co-implanted GaN samples were studied using X-ray diffraction, Raman scattering and superconducting quantum interference device techniques. XRD studies of non-implanted, Mn-implanted and co-implanted GaN samples showed the c-plane lattice constant was found to be 0.5181 nm, 0.5158 nm and 0.5181 nm respectively. The result revealed the expansion of GaN lattice due to the incorporation of Mn+2 ions in the samples. Raman spectra showed the peaks at 300 cm-1 and 670 cm-1 assigned to vibrational modes of gallium and nitrogen vacancy related defects respectively. SQUID studies showed the enhancement in magnetic properties after co-implantation with silicon ion. The Curie temperature estimated from zero field and field cooled curves for Mn-implanted and co-implanted with silicon ion into GaN samples was found to 301 and 326 K
