OBSERVATION OF A WEAK FERROMAGNETIC GROUND-STATE STRUCTURE FOR THE LITHIUM-INSERTION COMPOUND LI2FE2(MOO4)(3)

The low-temperature magnetism and neutron structure of orthorhombic Li 2Fe2(MoO4)(3), synthesized via the topotactic redox-insertion reaction of LiI with Fe-2(MoO4)(3), is discussed, dc magnetic susceptibility m easurements in an applied field of 30 G, and very low field (H-o = 1 G ) ac susceptibility measurements (real and imaginary (out-of-phase) co mponents) show a weakly ferromagnetic state, below 12.5 K, that is mos t likely due to intrinsic canting of antiferromagnetically coupled lat tices, An analysis of the magnetic scattering from powder neutron diff raction data at 4.2 K shows an antiferromagnetic spin arrangement. Alt hough it was not possible to refine a small magnetic component that wo uld give rise to a net ferromagnetic moment, the magnetic space group symmetry permits a ferromagnetic component parallel to the x axis, whi ch accounts for the weak ferromagnetism observed in the susceptibility studies. (C) 1997 Academic Press.