Effect of Mg Shallow Doping on Structural and Magnetic Properties of LiFePO4 Triphylite

We examine the structural and magnetic properties of Mg shallow-doped LiMg _x Fe _1−x PO ₄ ( ${x} =0.01$ , 0.05, and 0.1) samples synthesized by the conventional solid-state reaction route. Rietveld refinement of the X-ray diffraction patterns shows the crystal structure and bond lengths of LiO ₆ and Fe(Mg)O ₆ . The Néel temperature ( ${T} _{\text {N}}$ ), spin reorientation temperature ( ${T} _{\text {S}}$ ), Curie–Weiss temperature, and effective moment decreased owing to the decrease in superexchange interactions with increasing Mg ²⁺ ions. The Mössbauer spectra of samples below ${T} _{\text {N}}$ were fitted with asymmetrical eight absorption lines, whereas above ${T} _{\text {N}}$ were fitted with symmetrical doublet. The change in the value of electric quadrupole splitting and its slop of magnetic susceptibility at ${T} _{\text {S}}$ suggests that spin reorientation related to the orbital angular moment contributes to the magnetic properties by spin–orbit coupling. The value of isomer shift of samples at all temperatures was Fe ²⁺ ion states and it decreased with increasing Mg ²⁺ ion owing to decrease in charge density at the Fe nucleus due to the presence of Mg ²⁺ ions on the FeO ₆ site.