26 research outputs found
Multipole tensor analysis of the resonant x-ray scattering by quadrupolar and magnetic order in DyB2C2
Resonant x-ray scattering (RXS) experiment has been performed for the (3 0
1.5) superlattice reflection in the antiferroquadrupolar and antiferromagnetic
phase of DyB2C2. Azimuthal-angle dependence of the resonance enhanced
intensities for both dipolar (E1) and quadrupolar (E2) resonant processes has
been measured precisely with polarization analysis. Every scattering channel
exhibits distinctive azimuthal dependence, differently from the symmetric
reflection at (0 0 0.5) which was studied previously. We have analyzed the
results using a theory developed by Lovesey et al., which directly connects
atomic tensors with the cross-section of RXS. The fitting results indicate that
the azimuthal dependences can be explained well by the atomic tensors up to
rank 2. Rank 3 and rank 4 tensors are reflected in the data very little. In
addition, The coupling scheme among the 4f quadrupolar moment, 5d ortitals, and
the lattice has been determined from the interference among the Thomson
scattering from the lattice distortion and the resonant scatterings of E1 and
E2 processes. It has also been established from the RXS of the (3 0 1.5)
reflection that the canting of the 4f quadrupolar moments exists up to T_Q. We
also discuss a possible wavefunction of the ground state from the point-charge
model calculation.Comment: 9 pages, 10 figure
Microscopic Approach to Magnetism and Superconductivity of -Electron Systems with Filled Skutterudite Structure
In order to gain a deep insight into -electron properties of filled
skutterudite compounds from a microscopic viewpoint, we investigate the
multiorbital Anderson model including Coulomb interactions, spin-orbit
coupling, and crystalline electric field effect. For each case of
=113, where is the number of electrons per rare-earth ion, the
model is analyzed by using the numerical renormalization group (NRG) method to
evaluate magnetic susceptibility and entropy of electron. In order to make
further step to construct a simplified model which can be treated even in a
periodic system, we also analyze the Anderson model constructed based on the
- coupling scheme by using the NRG method. Then, we construct an orbital
degenerate Hubbard model based on the - coupling scheme to investigate
the mechanism of superconductivity of filled skutterudites. In the 2-site
model, we carefully evaluate the superconducting pair susceptibility for the
case of =2 and find that the susceptibility for off-site Cooper pair is
clearly enhanced only in a transition region in which the singlet and triplet
ground states are interchanged.Comment: 14 pages, 11 figures, Typeset with jpsj2.cl
Intra- site 4f-5d electronic correlations in the quadrupolar model of the gamma-alpha phase transition in Ce
As a possible mechanism of the phase transition in pristine
cerium a change of the electronic density from a disordered state with symmetry
Fm-3m to an ordered state Pa-3 has been proposed. Here we include on-site and
inter- site electron correlations involving one localized 4f-electron and one
conduction 5d-electron per atom. The model is used to calculate the crystal
field of -Ce and the temperature evolution of the mean-field of
-Ce. The formalism can be applied to crystals where quadrupolar
ordering involves several electrons on the same site.Comment: 12 pages, 2 figures, 4 tables, submitted to Phys. Rev.