Determination of magnetic structure in LiFe 1-xMn xPO 4 by neutron powder diffraction

Abstract

Lithium orthophosphates LiFe 1-xMn xPO 4 (x=0,0.2,0.4,0.6,0.8,1) were successfully synthesized using a solid state reaction method and characterized by X-ray powder diffraction, neutron powder diffraction and magnetic susceptibility measurement. Structure refinements against powder diffraction data were carried out in the orthorhombic space group Pnma. Magnetic susceptibility measurements showed all samples undergo AFM ordering at low temperature. Mn"2"+ doped in Fe-site resulted the below Néel temperature T_N decreased from 52 K (x=0) to 38 K (x=1). The magnetic structures from neutron powder diffraction data confirmed the AFM ordering with magnetic space group Pnma' for LiFePO"4 and all intermediate compounds, with a propagation vector k=(0 0 0). Only the pure LiMnPO_4 sample behaves differently showing an AFM ordering with magnetic space group Pn'm'a'. A weak ferromagnetic component in the c-direction also observed in LiMnPO 4.