Observation of the antiferroquadrupolar order inDyB2C2by resonant x-ray scattering

Abstract

We have investigated the antiferroquadrupolar ͑AFQ͒ order in DyB 2 C 2 by resonant x-ray scattering. X rays with energies near the L 3 absorption edge of Dy were employed. Superlattice peaks that correspond to three kinds of propagation vectors of ͑1 0 0͒, ͑1 0 1/2͒, and ͑0 0 1/2͒ were investigated in detail with polarization analyses. The experimental results are analyzed using a formalism of resonant x-ray scattering and a model of the AFQ order. The magnetic and quadrupolar scatterings are explained by the model satisfactorily. A detailed investigation of the critical behavior of the AFQ ordering is also reported. The critical exponent ␤ is deduced to be 0.35, not far from the three-dimensional Heisenberg system. We have also succeeded in detecting the diffuse scattering above T Q .

X-ray resonant scattering study of the structural and magnetic transitions inPrB6

“…However, in several systems electric quadrupole ͑E2͒ transitions are also significant, e.g., DyB 2 C 2 . 20 At the Pr L II edge the E1 transition connects 2p 1/2 → 5d states, while the E2 transition connects to the lower-energy 4f states.…”

Theory of Elastic Neutron Scattering by Ordered Magnetic Octupoles inf-Electron Systems

“…A similar situation may be found in DyB 2 C 2 where the O xy -like AFQ order is realized below 25K. 17) A direct observation of field-induced octupoles by neutron scattering is apparently a challenging future problem.…”

Octupole Ordering Phases and Elastic Neutron Scattering inf-Electron Systems

“…A similar situation may be found in DyB 2 C 2 , where the O xy -like AFQ order is realized on a tetragonal crystal below 25 K. 23) This material must be favorable for detecting the superlattice reflections due to octupole, because a large J can give a much larger local field. It can give an alternative information on the CF states and the multipolar interaction in addition to the results of the resonant X-ray scattering studies.…”

“…It can give an alternative information on the CF states and the multipolar interaction in addition to the results of the resonant X-ray scattering studies. 23,24) Finally, it should be noted that the present consideration is applicable also to inelastic neutron scattering for the systems with active multipole degrees of freedom. 25) In multipolar excitations with forbidden dipolar transition, there is a chance to observe an octupolar transition in the high-κ spectra.…”