Dual control on structure and magnetic properties of Mg ferrite: Role of swift heavy ion irradiation

Effect of swift heavy ion irradiation on MgFe2O4 (annealed at 450 °C/3 h) sample prepared by a sol-gel auto-combustion procedure has been studied. Single phase samples were irradiated with 120 MeV 28Si9+ with ion fluence: 1 × 1011, 1 × 1012, and 1 × 1013 ions/cm2 to monitor its effect on the structure, cation distribution, and magnetic properties. Electronic energy loss induced modifications of cation distribution, structural, magnetic properties were examined by XRD, VSM, FE-SEM, and EDS. XRD measurements show the formation of single phase nanocrystalline mixed cubic spinel structure (grain size 31-35 nm). Observed slight changes of experimental lattice parameter with increasing irradiation dose is ascribable to the migration of Mg2+ ions (ionic radius: 0.071 nm) from B to A site with simultaneous migration of Fe3+ ions (ionic radius: 0.063 nm) from A to B site. Sample irradiated at a lower fluence (1 × 1011 ions/cm2) has higher specific surface area (S), is more suitable for catalytic activity. Irradiation leads formation of dead layer, thus affects magnetic properties, via spin canting at surface. Therefore, irradiation can be used to control both structural, magnetic properties. SEM images display agglomerated nano-particles, while EDS pattern confirms the presence of Mg, Fe and O elements in the sample. First time the antistructural modeling for magnesium ferrite is reported to get information on active surface centers.