The effect of proton irradiation on magnetic properties of lithium ferrites

The effect of proton irradiation on magnetic properties of lithium ferrites has been investigated with x-ray diffraction (XRD), magnetization, and Mössbauer spectroscopy measurements. Li 0.5 Fe 2.5 O 4 powders have been fabricated by the sol-gel method. Following the annealing at 700 ° C , these samples have been proton irradiated with 1, 5, and 10 pC / μ m 2 . The analysis of XRD patterns by Rietveld refinement method shows that these samples have ordered cubic spinel structures with space group of P 4 3 32 . We have observed that the corresponding lattice constant a 0 linearly increases from 8.3301 to 8.3314 ± 0.0001 Å with increasing proton irradiation. Compared to nonirradiated sample, which has the saturation magnetization ( M s ) of 66.4 emu/g and oxygen occupancy of 3.9980 at room temperature, the values of magnetization and oxygen occupancy at room temperature are 66.0, 62.6, and 60.8 emu/g and 3.9840, 3.9452, and 3.9272, respectively, for 1, 5, and 10 pC / μ m 2 irradiated powders. Also, the coercivity ( H c ) decreases from 175.6 to 154.0 Oe with increasing proton irradiation. The Mössbauer spectra taken at room temperature show that the values of isomer shift ( δ ) for the tetrahedral ( A ) and octahedral ( B ) sites are consistent with the Fe 3 + valence state. The results suggest that the proton irradiation induces the oxygen vacancy defects, which in turn leads to the changes in magnetic properties.