Evidence of antiferroquadrupolar ordering of DyB₂C₂

Abstract

The antiferroquadrupolar ordering in DyB2C2 has been investigated using the x-ray resonant scattering technique. The dependence of the intensities of two superlattice peaks on temperature, azimuthal angle, and energy of the incident x-rays was measured. The results show that the antiferroquadrupole ordering, which accompanies a structural phase transition, exists below TQ = 25 K. A structural model for the antiferroquadrupole ordering, for which the propagation vectors are (0,0,1/2) and (0,1,1/2), is presented.

Resonant x-ray scattering spectra from multipole ordering: NpM4,5edges inNpO2

“…36,37,38,39,40,41,42,43 The intermediate state is created by the transition from the 2p-core to 5d states. Since the 5d states are considerably delocalized with forming energy bands, the assumption that the intermediate state preserves the rotational invariance becomes less accurate.…”

X-ray birefringence and dichroism obtained from magnetic materials

“…For a saturated ion the atomic quantities in (69) are zero apart from hA zz i and using in (54) the values hQ 0 i À15a2, hP 0 i = 5/2 and hR 0 i 0 we ®nd 3a2 1a2 hA zz i À3a140 À2 " J 1 AE 8a3 È É X Experiments of the type proposed here are very much complementary to studies of forbidden resonant diffraction (e.g. Tanaka et al, 1999;Hirota et al, 2000), which can yield quite direct evidence for quadrupole orbital ordering. The linear dichroism signal in (69) provides, instead, information about the average quadrupole moments: of special interest here might be, for example, any changes observed at the phase transitions.…”

“…Two groups of researchers, using resonant X-ray Bragg diffraction near the Dy L 3 edge, have reported compelling evidence in favour of an AFQ con®guration (Tanaka et al, 1999;Hirota et al, 2000). However, not all issues are settled.…”

“…Below T Q the crystal adopts a lower symmetry for which Tanaka et al (1999) have proposed the space group P4 2 /mnm, with dyprosium ions occupying sites 4(c) that have symmetry 2/m. In consequence, the value of hA 88 i is the same for every Dy ion and the quadrupole ordering is revealed in the relative signs of hA $$ À A i and hA $ i.…”

Studies on X-ray Thomson Scattering from Antiferroquadrupolar Order in TmTe

“…For example, the AFQ ordering phases in CeB 6 and DyB 2 C 2 are investigated in detail by means of RXS [3][4][5][6][7] and Thomson 1/18 scattering. 4,[8][9][10] On the other hand, the situation of TmTe may still be rudimentary.…”