The Effect of Lithium Intercalation on the Crystal Structure and Magnetic Property of Layered FeWO₄Cl

LiFeWO₄Cl has been prepared by reductive intercalation of lithium into FeWO₄Cl. FeWO₄Cl crystallizes into a tetragonal system (space group P4/nmm) with cell dimensions of a=6.677(5) Å and c=5.270(5) Å, while lithium intercalation gives rise to the formation of a monoclinic phase ( P2₁/m) with cell dimensions of a=7.050(0) Å, b=6.926(2) Å, c=5.043(0) Å and β=92.54(2)°. Infrared (IR) spectroscopic analyses of FeWO₄Cl and LiFeWO₄Cl show that the symmetry of the tetrahedral WO₄^2- group in FeWO₄Cl becomes reduced as the lithium intercalate into its two-dimensional lattice, indicating an alternately ordered lithium occupancy of half of the octahedral interlayer sites. The effective magnetic moments of FeWO₄Cl and LiFeWO₄Cl were estimated to be 5.95 and 5.10 B.M., respectively, which can be attributed to the selective reduction of a high-spin ferric ion to a high-spin ferrous one upon lithium intercalation. It was also found that the two-dimensional magnetic property of FeWO₄Cl was changed to a three-dimensional one in LiFeWO₄Cl owing to the c-axis contraction.