Effects of oxygen vacancy and local spin on the ferromagnetic properties of Ni-doped In2O3 powders

► The ferromagnetism of the (In1−xNix)2O3 powders can be switched “on” and “off” by alternate air and vacuum annealing. ► No ferromagnetism emerged in pure In2O3 powder regardless of any annealing process. ► XRD, TEM, FC/ZFC measurements indicated that the (In1−xNix)2O3 powders were single-phase. ► Oxygen vacancy and local spin are two indispensable factors for producing ferromagnetism in Ni-doped In2O3 system.