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
.