Crystal-Field Excitations, Magnetic-Field-Induced Phase Transition and Neutron-Scattering Spectra in PrOs_4Sb_<12>(Condensed Matter : Electronic Structure, Electrical, Magnetic and Optical Properties)

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One possible origin of the field-induced ordered phase (FIOP) in PrOs_4Sb_<12> is an interaction of quadrupolar moments of Pr 4f electrons in the singlet-triplet crystal-field (CF) levels. We study theoretically excitations and inelastic neutron-scattering (INS) spectra of this compound, based on the antiferro-quadrupolar (AFQ) interaction. It is pointed out that a unique feature of the AFQ model shows up in the momentum dependence of the INS spectra, which is in agreement with recent experiments. Then, it is shown that the spectral shape of INS is drastically changed with increasing magnetic field and changing field direction. The origin of this change is discussed in terms of a reconstruction of the CF states by the field and the FIOP. Finally, we report the properties of critical dynamics around the transition field to the FIOP. It is shown that the T_h, symmetry is relevant to the low-energy dynamics, giving anisotropic critical properties.
社団法人日本物理学会の論文
2004-12-15