Spin ordering between sub-lattices in nasicon Li3Fe2(PO4)3 measured by Mössbauer spectroscopy

The chemical stability and conductivity of nasicon-structured α-Li3Fe2(PO4)3 make it a possible candidate for a cathode material in Li-battery. The x-ray diffraction pattern of Li3Fe2(PO4)3 showed the monoclinic structure with space group of P21/n. In the zero-field-cooled (ZFC) curve, the magnetization remained constant while the temperature was increased up to the splitting temperature (TS = 11 K) of two sub-lattices, indicating the antiferromagnetic behavior below TS. Magnetization curves of both ZFC and FC from 4.2 to 295 K showed ferrimagnetic behavior below the Néel temperature (TN = 29.5 K). We observed the change in the slope of the temperature-dependent Hhf curve at TS. These results suggest that the change in the spin ordering in Li3Fe2(PO4)3 is originated from the difference in hyperfine interactions between the localized Fe3+ magnetic ions at each of two sub-lattices. The spectra of Li3Fe2(PO4)3 under applied magnetic field of 5 T exhibit the magnetic phase transition around TS, indicating antiferromagnetic behavior below TS and ferrimagnetic behavior between TS and TN.