Development of wide band gap semiconductor with ferromagnetic properties over a wide temperature range is a long standing demand for their applications in multifunctional spintronic devices. We present ferromagnetic semiconductor properties in Al2O3 system, which is electrically an insulator and non-magnet, by modifying lattice structure and lattice defects in the process of non-magnetic Ga ion doping, Ag ion beam irradiation, and implantation of ferromagnetic (Fe, Co) metal ions in bulk and thin film samples. The samples in Rhombohedral structure (R \(\overline{3 }\) c space group) were used for studying structural, electrical, optical and magnetic properties. X-ray photoelectron spectroscopy was used for information of the surface chemical state (elemental composition, chemical bonding, charge state of the ions, defects and vacancy) of the samples. The SRIM (Stopping and Range of Ions in Matter) calculations were used to estimate the ion-beam induced defects. The optical band gap values in the range of 3.6–4.5 eV confirmed wide band gap semiconductor nature of the samples. The ferromagnetic properties at room temperature were confirmed through magneto-optic Kerr effect (surface magnetic coercivity 530–850 Oe) and dc magnetic measurement (bulk magnetic coercivity 25–106 Oe and saturated magnetization 0.09–37 memu/g). The enhancement of ferromagnetic properties in Al2O3 based samples have been understood in terms of defect induced local spin order at the surface and bulk structure of the samples, activated during material synthesis.
