Low-field magnetoresistance and magnetic study of Ba/sub 2/Fe/sub 1+x/Mo/sub 1-x/O/sub 6/

We have investigated low-field magnetoresistance (MR) and magnetic properties of Ba/sub 2/Fe/sub 1+x/Mo/sub 1-x/O/sub 6/ (x=0-0.2) to point out some effects of Fe-Mo disorder between the Fe and Mo ions. Polycrystalline samples have been prepared by the conventional solid-state reaction in a stream of 5% H/sub 2/-Ar gas. X-ray data indicate that the symmetry is cubic and the data are compatible with the Fm3m space group. All samples are single phase and exhibit a series of superstructure-reflection lines due to cation order of Fe and Mo. The magnitude of the negative MR is 2.9% for x=0 and 1.5% for x=0.2 at room temperature with magnetic fields of 7 kOe. Saturation magnetization is 2.8 /spl mu//sub B//f.u. for x=0.2 which is smaller than the value of 3.8 /spl mu//sub B//f.u. for x=0. This large variation of magnetization between x=0 and 0.2 arises from the disorder at the Fe and Mo sites.