Effects of carrier doping on Curie temperature in double perovskite Ba2FeMoO6

We have investigated the effects of the partial substitution of K1+ for Ba2+ on the magnetic properties of the double perovskite Ba2FeMoO6 (BFMO). Polycrystalline Ba2-x K x FeMoO6 samples have been prepared by the conventional solid-state reaction in a stream of 5% H2/Ar gas. Magnetization (15 K, 7 kOe) is 3.4 μ B/f.u. for x=0.2 which is smaller than the value of 3.8 μ B/f.u. for x=0. This decrease of magnetization arises from the disorder at the Fe and Mo sites. The magnetic transition temperature T c decreases from 316 K for x=0 to 260 K for x=0.2 at a rate of 5.6 K/% with increasing x. The decrease of T c with K+ doping is associated with carrier doping, which is consistent with the result of La3+ doping in BFMO