Neutron Diffraction and Mössbauer Studies of LiFePO4

Chan Hyuk Rhee, In Kyu Lee, Seung Je Moon, Sam Jin Kim and Chul Sung Kim

J. Korean Phys.Soc. 58,472 [doi: 10.3938/jkps.58.472 | PDF Download]

The crystal structure of LiFePO4 has been determined to be orthorhombic (Pnma) from neutron diffraction measuerment. The temperature dependence of the magnetization was measured by using a SQUID magnetometer. The microscopic interaction was investigated with 57Fe Mössbauer spectroscopy. At temperature below TN = 51 K, LiFePO4 exhibited an anti-ferromagnetic behavior while at temperature below 23 K, we observed abrupt increase in magnetization and magnetic hyperfine field (Hhf). The electric quadrupole splitting (ΔEQ) reached its maximum value at 23 K and decreases steadily with decreasing temperature below 23 K. This indicated that the orbital angular momentum L was quenched by strong crystalline field in the asymmetric octahedral structure at temperature above 23 K. ΔEQ decreased due to spin-orbit coupling, and the orbital angular moment contribution enhances Hhf at temperatures below 23 K.