Effect of cobalt on the magnetic properties of the LiFe1-xCoxO2 layered system (0≤x≤1)

Layered LiFe1-xCoxO2 was prepared in the whole composition range by ion-exchange reaction in a molten eutectic mixture of LiCl and LiNO3 at 260 degreesC, The magnetic properties were studied by means of magnetic susceptibility and high-field magnetization measurements. Layered LiFeO2 exhibits a Neel temperature of T-N=20 K. Some cationic disorder is present but seems to have no effect on the magnetic properties. The saturation magnetization and the number of effective Bohr magnetons are consistent with the high spin state (S = 5/2) of the Fe3+ ion. A two sublattice model consisting of antiferromagnetic order between ferromagnetic layers is proposed with an estimation of the ferro- and antiferromagnetic interactions. Replacing iron by cobalt leads to an increase of the Weiss temperature theta up to x = 0.4 but at the same time the antiferromagnetic long-range order is destroyed. The effect of cobalt on the superexchange interactions is also discussed. (C) 2000 Academic Press.