Using vibrating sample magnetometery (VSM) 50MeV Li 3+ ion irradiation effects on magnetic properties of single crystals of SrGa x In y Fe 12−( x + y ) O 19 (where x=0, 5, 7, 9; y=0, 0.8, 1.3, 1.0), are reported. The substitution of Ga and In in strontium hexaferrite crystals decreases the value of magnetization sharply, which is attributed to shifting of collinear magnetic order to a non-collinear one. Reduction of magnetization is also explained to be as a result of the occupation of the crystallographic sites of Fe 3+ by Ga 3+ and In 3+ . The Li 3+ ion irradiation decreases the value of magnetization, irrespective of whether the crystals are Ga–In substituted or unsubstituted crystals of SrFe 12 O 19 . The result is interpreted in terms of the occurrence of a paramagnetic doublet in crystals replacing magnetic sextuplet as a result of irradiation. Substitution of Ga–In in Strontium hexaferrite decreases the value of anisotropy constant. Irradiation with Li 3+ ions increases the values of anisotropy field for both substituted as well as unsubstituted crystals. Substitution with Ga–In also decreases the Curie temperature (T c ) but the irradiation with Li 3+ ions does not affect the curie temperature of either Ga–In substituted or pure SrFe 12 O 19 crystals.