Antiferro--quadrupolar structures in UPd${}_3$ inferred from x-ray resonant Bragg diffraction

Abstract

A systematic analysis of resonant x-ray Bragg diffraction data for UPd${}_3$, with signal enhancement at the U M${}_{IV}$ edge, including possible structural phase-transitions leads to a new determination of the space groups of the material in the phases between $T_0=7.8$ K and $T_{+1}$ = 6.9 K as P222${}_1$ and between $T_{-1}$ = 6.7 K and $T_2$ = 4.4 K as space group P2${}_1$. In addition, the quadrupolar order-parameters, $<Q_{ab}>$, inferred from diffraction data in the phase between $T_{-1}$ and $T_2$, are $<Q_{xz}>$ and $<Q_{yz}>$ at the (103) Bragg reflection, and $<Q_{xy}>$ at the (104) reflection.

13 pages, 4 figures