X-ray measurement for the orbital ordering materials

By using our developed X-ray measurement system for powder sample below 1 K, we have studied the orbital ordering materials PrPtBi, Ce0.75La0.25B6 and PrPb3. The ground state of Pr3+ ion in the cubic semiconductor compound PrPtBi, is a nonmagnetic Γ3 doublet. To investigate whether the phase transition at 1.35 K is antiferro-quadrupolar (AFQ) or ferro-quadrupolar type ordering, we have studied this compound by X-ray measurement. Below the transition temperature we could not observe the splitting of any reflection lines but the full-width at half-maximum increases with decreasing temperature, which suggests the phase transition at 1.35 K is AFQ ordering. In this paper we also report the integrated intensity of (4 0 0) reflection as a function of temperature. This is the first experiment to investigate the AFQ ordering using ordinary X-ray diffraction method