Magnetic properties of barium uranate Ba2U2O7

Unique magnetic properties of a ternary uranate Ba2U2O7 are reported. Magnetic susceptibility measurements reveal that this compound undergoes a magnetic transition at 19 K. Below this temperature, magnetic hysteresis was observed. The results of the low-temperature specific heat measurements below 30 K support the existence of the second-order magnetic transition at 19 K. Ba2U2O7 undergoes a canted antiferromagnetic ordering at this temperature. The magnetic anomaly which sets in at 58 K may be due to the onset of one-dimensional magnetic correlations associated with the linear chains formed by U ions. The analysis of the experimental magnetic susceptibility data in the paramagnetic temperature region gives the effective magnetic moment μeff=0.73 μB, the Weiss constant θ=−10 K, and the temperature-independent paramagnetic susceptibility χTIP=0.14×10−3 emu/mole. The magnetic susceptibility results and the optical absorption spectrum were analyzed on the basis of an octahedral crystal field model. The energy levels of Ba2U2O7 and the crystal field parameters were determined.