Direct evidence of the spatial ordering of Dy 4f quadrupole and hexadecapole moments in DyB2C2 is demonstrated by resonant x-ray diffraction enhanced by an electric quadrupole event (E2 resonance) at the Dy LIII absorption edge. The diffraction data show that the structural phase transition at TQ = 24.7K is accompanied by a reduction in the symmetry of the Dy site to 2/m, from 4/m, and the spatial ordering of the time-even Dy multipoles with Ag character. Below TQ the crystal structure is described by the space group P4 2/mnm and Dy ions occupy sites (4c). The distortion at TQ involves the lattice occupied by B and C ions, and it amounts to a buckling of B-C planes that are normal to the two-fold rotation axis of 2/m. An immediately plausible model of low-energy Dy states correlates data on the specific heat, our x-ray diffraction signals, and magnetic ordering below 15.3 K which has been observed in magnetic neutron diffraction.
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|Publication status||Published - 2004 Jan 29|
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics