ABSTRACT
Spin dynamics in the new Kondo insulator compound CeRu2Al10 has been studied using unpolarized and polarized neutron scattering on single crystals. In the unconventional ordered phase forming below T0=27.3 K, two excitation branches are observed with significant intensities, the lower one of which has a gap of 4.8±0.3 meV and a pronounced dispersion up to ≈8.5 meV. Comparison with random-phase approximation magnon calculations assuming crystal-field and anisotropic exchange couplings captures major aspects of the data, but leaves unexplained discrepancies, pointing to a key role of direction-specific hybridization between 4f and conduction band states in this compound.
ABSTRACT
A mysterious antiferroquadrupolar ordered phase of CeB6 is considered as originating from the Txyz-type magnetic octupole moment in magnetic fields. By resonant x-ray diffraction, we have verified that the Txyz-type octupole is indeed induced in the 4f orbital of Ce with a propagation vector (1/2,1/2,1/2), thereby supporting the theory. We observed an asymmetric field dependence of the intensity for an electric quadrupole (E2) resonance when the field was reversed and extracted a field dependence of the octupole by utilizing the interference with an electric dipole (E1) resonance. The result is in good agreement with that of the NMR-line splitting, which reflects the transferred hyperfine field at the boron nucleus from the anisotropic spin distribution of Ce with an Oxy-type quadrupole.
