Synthesis and magnetic properties of LiFePO4 substitution magnesium

Abstract LiFe 0.9 Mg 0.1 PO 4 sample was prepared by using a solid–state reaction method, and the temperature-dependent magnetic properties of the sample were studied. The X-ray diffraction (XRD) pattern showed an olivine-type orthorhombic structure with space group Pnma based on Rietveld refinement method. The effect of Mg substitution in antiferromagnetic LiFe 0.9 Mg 0.1 PO 4 was investigated using a vibrating sample magnetometer (VSM) and Mossbauer spectroscopy. The temperature-dependence of the magnetization curves of LiFe 0.9 Mg 0.1 PO 4 shows abnormal antiferromagnetic behavior with ordering temperature. Sudden changes in both the magnetic hyperfine field ( H hf ) and its slope below 15 K suggest that magnetic phase transition associated to the abrupt occurrence of spin-reorientation. The Neel temperature ( T N ) and spin-reorientation temperature ( T S ) of LiFe 0.9 Mg 0.1 PO 4 are lower than those of pure LiFePO 4 ( T N  = 51 K, T S  = 23 K). This is due to the Fe–O–Fe superexchange interaction being larger than that of the Fe–O–Mg link. Also, we have confirmed a change in the electric quadrupole splitting (ΔE Q ) by the spin-orbit coupling effect and the shape of Mossbauer spectrum has provided the evidence for T S and a strong crystalline field. We have found that Mg ions in LiFe 0.9 Mg 0.1 PO 4 induce an asymmetric charge density due to the presence of Mg 2+ ions at the FeO 6 octahedral sites.