Interference between thomson scattering and resonant scattering in X-ray diffraction from CeB

CeBのX線回折におけるトムソン散乱と共鳴散乱の干渉

長尾 辰哉*; 五十嵐 潤一

Nagao, Tatsuya*; Igarashi, Junichi

CeBの反強四重極秩序相におけるL吸収端近傍の共鳴散乱とトムソン散乱の両方の過程を考慮してX線回折の機構を理論的に研究した。格子歪み無しで、4f状態の反強四重極秩序相での電荷の異方性から実験に対応するトムソン散乱強度を計算で得る事ができた。この大きさはL吸収端近傍で共鳴散乱強度と同程度になり、二つの項は干渉を示すことを見いだした。これは、実験事実とよく対応する。これらの結果から、共鳴散乱及びトムソン散乱の両方とも反強四重極秩序の直接の反映であると結論される。

We examine the mechanism of the X-ray diffraction process by including the Thomson scattering (TS) term in addition to the resonant X-ray scattering (RXS) term near the Ce L absorption edge in the antiferroquadrupole (AFQ) ordering phase of CeB. Assuming the AFQ order in the 4f states but without any lattice distortion, we obtain the TS intensity comparable to the RXS intensity, owing to the anisotropic charge distribution of 4f states. The present calculation reproduces well the interference pattern between the TS and RXS terms for the (5/2,3/2,3/2) spot observed in the recent experiment. The result suggests that the TS signal as well as the main peak of the RXS signal are a direct reflection of the AFQ order in CeB.