Investigation of Microscopic Crystal Field in Co-Doped Lithium-Iron Phosphate

We present the study on the structural and the magnetic properties of LiFePO 4 and LiFe 0.8 Co 0.2 PO 4 . The crystal structure was determined to be orthorhombic with space group P nma by Rietveld refinement method. We have observed the increase in the lattice constants with Co 2+ ion substituted. The Mossbauer spectra of olivine LiFePO 4 and LiFe 0.8 Co 0.2 PO 4 have shown distorted line broadening below T N . In order to explain the observed line broadening, we have analyzed the Mossbauer spectra by considering the full Hamiltonian for the 57 Fe nucleus, and both the magnetic dipole and the electric quadrupole interactions. Also, we have observed the anomalous change in the electric quadrupole splitting near the T N .