Neutron scattering studies of order parameters and excitations in antiferro-quadrupolar phase of PrFe4P12

The order parameters in the antiferro-quadrupolar (AFQ) ordered phase of PrFe4P12 have been investigated by polarized neutron diffraction measurement. By observing the interference effect of scattering amplitudes from the Fe-ion displacement and the antiferromagnetic component induced by the magnetic field applied along the [0,0,1] axis, we conclude that the dominant ordered quadrupole is O-2(0) in the low-temperature phase. By inelastic neutron scattering experiment for a single-crystal sample, we observed sharp magnetic excitations in the AFQ-ordered phase, whose maximum intensity appears at the Brillouin zone center and minimum at the zone boundary. This fact indicates the existence of ferromagnetic correlation between Pr ions in the AFQ-ordered phase. (c) 2005 Elsevier B.V. All rights reserved.