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 μ_eff=0.73 μ_B, the Weiss constant θ=−10 K, and the temperature-independent paramagnetic susceptibility χ_TIP=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.