Modifications in magnetic anisotropy of M—type strontium hexaferrite crystals by swift heavy ion irradiation

Using vibrating sample magnetometery (VSM) 50 MeV 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 12O 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 12O 19 crystals.