Ba2U2O7 : A canted ferromagnet with double-perovskite related orthorhombic structure

Ba2U2O7 with double-perovskite related orthorhombic structure has been prepared by reducing BaUO4 in H2 (He) atmosphere. The magnetic susceptibility (χ) measurement has revealed that this system undergoes successive magnetic transitions, first at T N'=60 K and then at T N=19 K. The 1/χ vs. temperature (K) data above T N' gives the following characteristic magnetic parameters: μP (eff)=0.73μB, θW=-10 K, and χ0 (TIP)=0.00014, which are all reasonable for the two kinds of U5+ (5f1) ions in the distorted octahedral sites. The magnetization (M) vs. magnetic field (H) data at 2 K exhibited a clear hysteresis loop, however, its M value at H=5.5 T is small (∼0.03-4 μB/U), not reaching saturation. These results suggest that Ba2U2O7 is a canted ferromagnet